Characteristics of an ovariectomized osteopenic rat model

Lycopene prevents bone loss in ovariectomized rats and increases the number of osteocytes and osteoblasts

Osteoporosis is a prevalent disease with a high incidence in women at the onset of menopause mainly because of hormonal changes, genetics, and lifestyle, leading to decreased bone mass and risk of fractures. Maintaining bone mass is a challenge for postmenopausal women, with calcium-rich food intake being essential for bone health. Nevertheless, other nutrients such as carotenoids may influence bone metabolism because of their high antioxidant properties. This study aimed to evaluate the effect of the carotenoid lycopene on bone cells and in the microarchitecture of ovariectomized rats employing in vitro and in vivo assays. After 8 weeks of ovariectomy, femurs were removed to isolate bone marrow mesenchymal cells to be cultured in osteogenic medium (sham and ovariectomized/OVX) or with 1 μmol/L lycopene (OVX/Lyc). There were performed assays for alkaline phosphatase activity and its in situ detection, mineralization nodules, and quantitative expression of genes associated with osteogenesis. Daily ingestion of 10 mg/kg of lycopene by oral gavage for 8 weeks after ovariectomy was conducted for stereological evaluation of the number and volume of osteoblasts, osteoclasts, and osteocytes of femur distal epiphysis and for microtomographic evaluation of the bone microarchitecture of the femoral proximal epiphysis. Data were normalized and analyzed by comparison among the groups using one-way ANOVA followed by post hoc tests with the significance level set out at 5%. Results showed that lycopene promoted an increase in ALP in situ detection as well as a significant increase in mineralized nodules deposition and expression of genes Runx2 and Bglap when compared with the OVX group. The administration by oral gavage of lycopene increased the total number of osteoblasts and osteocytes when compared to sham and ovariectomized groups. Additionally, it decreased the volume and number of osteoclasts and also reduced the volume of osteocytes compared to the sham group. These results suggest that lycopene improves bone cell metabolism and bone remodeling with the onset of osteoporosis. Future studies with different concentrations and periods of administration should be carried out to shed further light on it.

Anti-Osteoporosis Effects of the Fruit of Sea Buckthorn (Hippophae rhamnoides) through Promotion of Osteogenic Differentiation in Ovariectomized Mice

The fruit of Hippophae rhamnoides has been widely used for medicinal purposes because of its anti-inflammatory, antioxidant, antiplatelet, and antimicrobial effects. Since there are no clear reports on the therapeutic efficacy of H. rhamnoides in osteoporosis, this study aimed to confirm the potential use of H. rhamnoides for the treatment of osteoporosis through its osteogenic differentiation-promoting effect in ovariectomized mice. Through an in vitro study, we compared the effects of the EtOH extract of H. rhamnoides fruits (EHRF) on the differentiation of C3H10T1/2, a mouse mesenchymal stem cell line, into osteoblasts based on alkaline phosphatase (ALP) staining and the relative expression of osteogenesis-related mRNAs. The EHRF significantly stimulated the differentiation of mesenchymal stem cells into osteoblasts and showed 7.5 times (* p < 0.05) higher osteogenesis than in the untreated control. A solvent fractionation process of EHRF showed that the hexane-soluble fraction (HRH) showed 10.4 times (** p < 0.01) higher osteogenesis than in the untreated control. Among the subfractions derived from the active HRH by preparative HPLC fractionation, HRHF4 showed 7.5 times (* p < 0.05) higher osteogenesis than in the untreated naïve cells, and HRH and HRHF4 fractions showed 22.6 times (*** p < 0.001) stronger osteogenesis activity than in the negative control. Osteoporosis was induced by excision of both ovaries in 9-week-old female ICR mice for in vivo analysis, and two active fractions, HRH and HRHF4, were administered orally for three months. During the oral administration period, body weight was measured weekly, and bone mineral density (BMD) and body fat density were measured simultaneously using a DEXA machine once a month. In particular, during the in vivo study, the average BMD of the ovariectomized group decreased by 0.0009 g/cm2, whereas the average BMD of the HRH intake group increased by 0.0033 g/cm2 (* p < 0.05) and that of the HRHF4 intake group increased by 0.0059 g/cm2 (** p < 0.01). The HRH and HRHF4 intake groups significantly recovered the mRNA and protein expression of osteogenic genes, including ALP, Osteopontin, Runx2, and Osterix, in the osteoporosis mouse tibia. These findings suggest that the active fractions of H. rhamnoides fruit significantly promoted osteoblast differentiation in mesenchymal stem cells and increased osteogenic gene expression, resulting in an improvement in bone mineral density in the osteoporosis mouse model. Taken together, H. rhamnoides fruits are promising candidates for the prevention and treatment of osteoporosis.

Metabolomics and physiological analysis of the effect of calcium supplements on reducing bone loss in ovariectomized rats by increasing estradiol levels

BACKGROUND

Data from the 2010-2012 Chinese National Nutrition and Health Survey showed that the vast majority of postmenopausal women in China had dual deficiencies in calcium and estrogen.

OBJECTIVE

This study aimed to clarify whether calcium supplementation alleviated bone loss caused by calcium restriction combined with estrogen deficiency in rats.

METHODS

Forty-eight female rats aged 9 weeks were assigned to 4 groups and fed a low-calcium diet: sham-operated (SHAM-LC), ovariectomized (OVX-LC), and ovariectomized rats treated with 750 mg/kg (OVX-LC-M) or 2800 mg/kg CaCO3 (OVX-LC-H). CaCO3 or distilled water was administered orally for 13 weeks. Bone mineral density (BMD) and histomorphometry of the femur, serum biochemical parameters, and serum metabolites were analyzed.

RESULTS

The OVX-LC rats showed a significant increase in body weight and serum levels of lipid markers, a significant decrease in serum estradiol, calcium, phosphorus, and 25(OH)D levels, and deterioration of the femur. At 750 mg/kg and 2800 mg/kg, CaCO3 reduced the deterioration of trabecular bone and increased the trabecular area percentage (Tb.Ar %) and BMD of the femur. Serum estradiol levels increased in a dose-dependent manner after CaCO3 supplementation (p < 0.01). The administration of 2800 mg/kg CaCO3 decreased serum triglyceride and high-density lipoprotein levels (p < 0.05) and decreased the levels of the bone turnover markers osteocalcin, N-telopeptide of type I collagen and β-crosslaps. The results of the metabolomics analysis showed that the glycerophospholipid metabolism pathway was closely related to calcium supplementation, and more DG (44:6 n3), LysoPC (22:2) and PE (P-34:3) and less Cer (d43:0) and PE-NMe2 (46:3) were produced.

CONCLUSIONS

The results clearly indicated that calcium supplementation was beneficial for decreasing bone loss in OVX-LC rats. The present study is the first to show that calcium supplementation increased the estradiol content in OVX-LC rats, and the effect of calcium on bone loss may be partially attributed to the increase in the estrogen level that subsequently induced the changes in metabolite levels, eventually increasing the bone mineral density to a relatively higher level to reduce bone deterioration.

Anti-osteoporotic effects of alisol C 23-acetate via osteoclastogenesis inhibition

Alismatis rhizoma (AR) is the dried rhizome of Alisma orientale (Sam.) Juz. (Alismataceae). This traditional Chinese formula is diuretic, hypoglycemic, and hypolipidemic. Alisol C 23-acetate (AC23A) from AR is anti-inflammatory and ameliorates certain metabolic diseases. However, the mechanism by which AC23A mitigates osteoporosis is unknown. The present study investigated the anti-osteoporotic effects of AC23A in vivo and in vitro. In an ovariectomized (OVX) rat model, AC23A ameliorated OVX-induced organ coefficients and trabecular bone loss. In OVX rats, AC23A treatment lowered serum TRAP5b, CTK, β-CTX, TNF-α, IL-6, and IL-1β, raised serum E2, and did not significantly change serum OCN or BALP. AC23A inhibited osteoclast formation in a rat co-culture system without affecting osteoblast activity. RANK (receptor activator of nuclear factor kappaB) signaling channels are vital osteoclastogenesis transcription elements. AC23A inhibited RANK ligand (RANKL)-induced TRAP, c-Fos, MMP9, NFATc1, and CTK expression and JNK phosphorylation. Therefore, AC23A is anti-osteoclastogenic in vitro and in vivo by inhibiting RANKL-induced osteoclast differentiation and function. Moreover, AC23A could help prevent or limit osteoclast-mediated bone diseases by inhibiting osteoclastogenesis.

Bone Measurements by Peripheral Quantitative Computed Tomography in Rodents

This chapter provides information for the in vivo use of peripheral quantitative computed tomography in rats and mice to determine bone density and cortical geometric data, including suggestions for study design, instrument setting, and data interpretation. This update also provides guidance for the use of pQCT to extract muscle and fat cross-sectional area information from the bone scans.

Effect of lycopene on titanium implant osseointegration in ovariectomized rats

Background

Lycopene prevents bone loss in osteopenic models. However, the role of lycopene in the success rate of dental implants under osteopenic conditions remains unknown. The aim of this study was to evaluate whether lycopene prevents delayed implant osseointegration in an ovariectomized (OVX) rat model.

Methods

Thirty female Sprague-Dawley rats were randomly divided into the following groups: OVX with vehicle (OVX group), OVX with lycopene (OVX + lycopene group) and sham-operated with vehicle (sham group). Twelve weeks after ovariectomy or sham operation, titanium implants were placed into the distal metaphysis of the bilateral femurs of each rat. These rats were subsequently gavaged with lycopene (50 mg/kg/day) or vehicle. After 12 weeks of gavage, all rats were sacrificed, and specimens were harvested. Sample osseointegration was evaluated by biomechanical testing, 3D micro-computed tomography (micro-CT) analysis and histomorphometric analysis.

Results

Compared with the OVX group, the OVX + lycopene group showed a 69.3% increase in the maximum push-out force (p < 0.01). Micro-CT data for the femurs in the OVX + lycopene group showed significantly higher bone volume, trabecular thickness and less trabecular space than did those in the OVX group. The bone area (BA) around the implant and bone contact (BC) with the implant were increased by 72.3% (p < 0.01) and 51.4% (p < 0.01) in the OVX + lycopene group, respectively, compared with those in the OVX group. There was no significant difference in the mechanical test, micro-CT scanning and histomorphometric data between the OVX + lycopene and sham groups (p > 0.05).

Conclusions

Lycopene improved implant osseointegration, fixation and bone formation under osteopenic conditions, suggesting that lycopene is a promising therapeutic agent to prevent delayed implant osseointegration and bone loss under osteopenic conditions.

An estradiol-independent BDNF-NPY cascade is involved in the antidepressant effect of mechanical acupuncture instruments in ovariectomized rats

Menopause-related depression devastates women's quality of life after middle age. Previous research has shown that estrogen hormone therapy has serious adverse effects; thus, complementary and integrative therapies have been considered clinically. The present study investigates whether stimulation of an acupoint using a mechanical acupuncture instrument (MAI) can mitigate depression-like behavior caused by estrogen deficiency in ovariectomized (OVX) rats. The animals were divided into Sham OVX, OVX, OVX + Sameumgyo (SP6) and OVX + NonAcu (non-acupuncture point) groups. MAI stimulation significantly increased the total distance traveled in the open-field test and the number of open-arm entries in the elevated plus maze and decreased the duration of immobility in the forced swim test. In addition to this decrease in depression-like behavior, brain-derived neurotrophic factor (BDNF) and neuropeptide Y (NPY) release increased in the hippocampus in response to MAI treatment, but estradiol levels did not recover. Furthermore, microinjection of the BDNF receptor antagonist ANA-12 (0.1 pmol/1 μl) into the hippocampus before MAI stimulation significantly suppressed the recovery of NPY levels. Taken together, these findings indicate that MAI stimulation at SP6 facilitates an estradiol-independent BDNF-NPY cascade, which may contribute to its antidepressant effects in OVX rats, an animal model of menopausal disorders.

Pre-clinical in vivo models for the screening of bone biomaterials for oral/craniofacial indications: focus on small-animal models

Preclinical in vivo experimental studies are performed for evaluating proof-of-principle concepts, safety and possible unwanted reactions of candidate bone biomaterials before proceeding to clinical testing. Specifically, models involving small animals have been developed for screening bone biomaterials for their potential to enhance bone formation. No single model can completely recreate the anatomic, physiologic, biomechanic and functional environment of the human mouth and jaws. Relevant aspects regarding physiology, anatomy, dimensions and handling are discussed in this paper to elucidate the advantages and disadvantages of small-animal models. Model selection should be based not on the 'expertise' or capacities of the team, but rather on a scientifically solid rationale, and the animal model selected should reflect the question for which an answer is sought. The rationale for using heterotopic or orthotopic testing sites, and intraosseous, periosseous or extraskeletal defect models, is discussed. The paper also discusses the relevance of critical size defect modeling, with focus on calvarial defects in rodents. In addition, the rabbit sinus model and the capsule model in the rat mandible are presented and discussed in detail. All animal experiments should be designed with care and include sample-size and study-power calculations, thus allowing generation of meaningful data. Moreover, animal experiments are subject to ethical approval by the relevant authority. All procedures and the postoperative handling and care, including postoperative analgesics, should follow best practice.

Experimental Control for the Ovariectomized Rat Model: Use of Sham Versus Nonmanipulated Animal

One of 2 models required by the U.S. Food and Drug Administration for registration of a treatment for osteoporosis, the ovariectomized (OVX) rat model, is widely used in scientific studies investigating sex hormone-deficient bone loss. The use of control nonhuman animals is critical because bone turnover may be affected by animal stress, use of anesthetic, and the mechanisms involved in wound healing. Historically, researchers have used sham-operated animals who undergo the same manipulations as the OVX rats, but ethical concerns require consideration of unmanipulated (unoperated) control animals to minimize animal distress and unnecessary procedures. Herein, we report the results of 3 studies including OVX, sham, and unmanipulated rats and the effects on bone mineral density and content (BMD/BMC) during 2 to 6 months postsurgery. Our data indicate that while OVX animals generally had lower BMD and BMC than animals in either of the control groups, no differences were observed between sham and unmanipulated animals at any of the time points assessed. However, because bone turnover is a long-term process, studies with longer duration and multiple endpoints are warranted to confirm these results.

Differences in vertebral, tibial, and iliac cancellous bone metabolism in ovariectomized rats

Bone histomorphometry is usually performed on the iliac bone in humans and the tibia or vertebrae in rats. Bone metabolism differences among skeletal sites may be problematic when translating experimental results from rats to humans, but data on such differences in rats are lacking. Therefore, we examined the differences in bone structure and metabolism among skeletal sites using the lumbar vertebra (LV), tibia, and iliac bone obtained from ovariectomized or sham-operated rats preoperatively and at various times from 3 days to 26 weeks postoperatively. The trabeculae were thicker in the LV, where bone metabolism was less active than at other sites, and numerous fine trabeculae were observed in the tibia, where bone metabolism was more active. The iliac bone structure and metabolism were intermediate between those of the tibia and LV. Ovariectomy induced lower bone volume and higher bone metabolism in all skeletal sites, but the changes were greatest and occurred earliest in the tibia, followed by the iliac bone and then LV. Ovariectomy caused changes in bone metabolic markers, which occurred earlier than those in bone tissue. Activation frequency (Ac.f) increased after ovariectomy. At week 26 in ovariectomized rats, Ac.f was highest in the tibia (3.13 N/year) but similar between iliac bone (0.87 N/year) and LV (1.39 N/year). Ac.f is reportedly 0.3-0.4 N/year in the iliac bone of postmenopausal women, suggesting that bone turnover in rats is several times higher than in humans. The reference values reported here are useful for translating experimental results from rats to humans.

Biomechanical Characteristics of Osteoporotic Fracture Healing in Ovariectomized Rats: A Systematic Review

Biomechanical tests are widely used in animal studies on osteoporotic fracture healing. However, the biomechanical recovery process is still unknown, leading to difficulty in choosing time points for biomechanical tests and in correctly assessing osteoporotic fracture healing. To determine the biomechanical recovery process during osteoporotic fracture healing, studies on osteoporotic femur fracture healing with biomechanical tests in ovariectomized rat (OVX) models were collected from PUBMED, EMBASE, and Chinese databases. Quadratic curves of fracture healing time and maximum load were fitted with data from the analyzed studies. In the fitted curve for normal fractures, the predicted maximum load was 145.56 N, and the fracture healing time was 88.0 d. In the fitted curve for osteoporotic fractures, the predicted maximum load was 122.30 N, and the fracture healing time was 95.2 d. The maximum load of fractured femurs in OVX rats was also lower than that in sham rats at day 84 post-fracture (D84 PF). The fracture healing time was prolonged and maximum load at D84 PF decreased in OVX rats with closed fractures. The maximum load of Wister rats was higher than that of Sprague-Dawley (SD) rats, but the fracture healing time of SD and Wister rats was similar. Osteoporotic fracture healing was delayed in rats that were < = 12 weeks old when ovariectomized, and at D84 PF, the maximum load of rats < = 12 weeks old at ovariectomy was lower than that of rats >12 weeks old at ovariectomy. There was no significant difference in maximum load at D84 PF between rats with an osteoporosis modeling time <12 weeks and > = 12 weeks. In conclusion, fracture healing was delayed and biomechanical property decreased by osteoporosis. Time points around D95.2 PF should be considered for biomechanical tests of osteoporotic femur fracture healing in OVX rat models. Osteoporotic fracture healing in OVX rats was affected by the fracture type but not by the strain of the rat.

Animal model for medication-related osteonecrosis of the jaw with precedent metabolic bone disease

Despite the fact that the medications used to treat abnormal bone conditions often induce osteonecrosis of the jaw (ONJ), previous attempts to establish an animal model for ONJ have shown insufficient consideration for this important prerequisite for the development of the disease. The purpose of this study was to establish an animal model with the most common metabolic bone disease, osteoporosis. Ninty-six rats were randomly divided into ovariectomy (Ov) group (n=48) and sham-operated group (n=48). Six weeks after Ov or sham surgery, rats in each group were subdivided into bisphosphonate group (n=36 each) and control group (n=12 each) and injected with zoledronic acid and normal saline, respectively, once a week. After additional 6weeks, surgical intervention was performed, and the injections were continued for 8 more weeks. The animals were then sacrificed for further macroscopic, histological, histomorphometric, radiological, and bone biomarker investigations. As histologically determined, the Ov group (77.8%) showed higher ONJ prevalence compared to the sham group (47.2%; P<0.05). Micro-structural and histomorphometric assessments revealed that rats with ONJ (ONJ group) presented with deteriorated bone architectures with higher necrotic bone fraction and lower number of osteoclasts (P<0.05). Compared to the sham-operated ONJ group, the Ov ONJ group showed significantly lower values of Tb.N, Tb.Sp, Conn.D, N.Oc/T.Ar, and TRACP 5b and CTX/TRACP (P<0.05). The ovariectomized rat model in this study successfully mimicked human ONJ lesions with an underlying bone disease and showed different bone characteristics than that of the previous ONJ model. Based on the differences, further researches for investigating pathophysiology of ONJ, including various pharmacological responses for deteriorated bone environment, are required.

Protective effect of porcine placenta in a menopausal ovariectomized mouse

Menopause is a significant physiological phase that occurs as women's ovaries stop producing ovum and the production of estrogen declines. Human placenta and some amino acids are known to improve menopausal symptoms. In this study, we investigated that porcine placenta extract (PPE) and arginine (Arg), a main amino acid of PPE, would have estrogenic activities in ovariectomized (OVX) mice as a menopause mouse model, human breast cancer cell line (MCF-7) cells, and human osteoblast cell line (MG-63) cells. PPE or Arg significantly inhibited the body weight and increased the vagina weight compared to the OVX mice. PPE or Arg ameliorated the vaginal atrophy in the OVX mice. The levels of 17β-estradiol and the activities of alkaline phosphatase (ALP) were significantly increased by PPE or Arg in the serum of OVX mice. Trabecular bone parameters such as bone mineral density and porosity were also improved by PPE or Arg in the OVX mice. In the MCF-7 and MG-63 cells, PPE or Arg significantly increased the cell proliferation, estrogen receptor β mRNA expression, and estrogen-response elements luciferase activity. Finally, PPE or Arg increased the activations of ALP and extracellular signal-regulated kinase 1/2 in the MG-63 cells. These results indicate that PPE or Arg would have estrogenic and osteoblastic activity. Therefore, PPE or Arg may be useful as new pharmacological tools for treating menopausal symptoms including osteoporosis. Free Korean abstract: A Korean translation of this abstract is freely available at http://www.reproduction-online.org/content/150/3/173/suppl/DC1.

Time course of influence by ovariectomy and calcium diet on bone properties in mice

This study was investigated the influence by ovariectomy (OVX) and calcium diet on bone properties in eighty-one female ICR strain mice with age of 5 weeks. The animals were randomly assigned to sham operation (SHAM), OVX, SHAM+low Ca intake (L.Ca) and OVX+L.Ca group. They were euthanized with lethal dose of pentobarbital sodium at day 50, 100 and 140 post-operatively. For determining the bone properties, both femur and tibial bones were excised from the hind limb, and removed off surrounding tissues. Thereafter, bone length, bone dry weight, and also mechanical strength and ash content of the bones were determined. The bone length on both femur and tibia was significantly longer in OVX group than in the other groups after 50 day of experiment, this situation was continued to the end of the experiment. Bone dry weight, mechanical strength, and ash content were significantly decreased by OVX and L.Ca over the time of the experiment, and those of OVX+L.Ca group were the lowest in all groups. OVX and L.Ca have a great potential for weakening the mechanical strength and have an additive effect when combined. OVX and L.Ca block the gain of bone mass.

Increased activity of osteocyte autophagy in ovariectomized rats and its correlation with oxidative stress status and bone loss

OBJECTIVES

The objectives of the present study were to investigate ovariectomy on autophagy level in the bone and to examine whether autophagy level is associated with bone loss and oxidative stress status.

METHODS

36 female Sprague-Dawley rats were randomly divided into sham-operated (Sham), and ovariectomized (OVX) rats treated either with vehicle or 17-β-estradiol. At the end of the six-week treatment, bone mineral density (BMD) and bone micro-architecture in proximal tibias were assessed by micro-CT. Serum 17β-estradiol (E2) level were measured. Total antioxidant capacity (T-AOC), superoxide dismutase (SOD) activity, catalase (CAT) activity in proximal tibia was also determined. The osteocyte autophagy in proximal tibias was detected respectively by Transmission Electron Microscopy (TEM), immunofluorescent histochemistry (IH), realtime-PCR and Western blot. In addition, the spearman correlation between bone mass, oxidative stress status, serum E2 and autophagy were analyzed.

RESULTS

Ovariectomy increased Atg5, LC3, and Beclin1 mRNA and proteins expressions while decreased p62 expression. Ovariectomy also declined the activities of T-AOC, CAT, and SOD. Treatment with E2 prevented the reduction in bone mass as well as restored the autophagy level. Furthermore, LC3-II expression was inversely correlated with T-AOC, CAT, and SOD activities. A significant inverse correlation between LC3-II expression and BV/TV, Tb.N, BMD in proximal tibias was found.

CONCLUSIONS

Ovariectomy induced oxidative stress, autophagy and bone loss. Autophagy of osteocyte was inversely correlated with oxidative stress status and bone loss.

New bone formation enhanced by ADSCs overexpressing hRunx2 during mandibular distraction osteogenesis in osteoporotic rabbits

Promoting new bone formation during distraction osteogenesis (DO) in elderly patients with osteoporosis is still a challenge. In this study, we investigated the effect of gene therapy using local Runt-related gene 2 on new bone formation during osteoporotic mandibular DO in rabbits. First, we successfully established a mandibular osteoporotic animal model by ovariectomizing rabbits. Second, the right mandibles of the osteoporotic rabbits were distracted after corticotomy. The distraction gap of the rabbits in Group A2 and B2 were injected with Adv-hRunx2-GFP-transfected adipose-derived stromal cells (ADSCs) and Adv-GFP-transfected ADSCs, respectively. Rabbits in Groups C2 (ovariectomized control) and D2 (sham surgery control) were injected with physiologic saline. New-generation bone tissue in the distraction gap was analyzed via plain radiographic examinations, micro-computed tomography, histological examinations, and biomechanical testing at weeks 3, 6, and 9 of the consolidation period. Results of above examinations showed that no ideal new bone formation was observed in Groups B2 and C2, but obvious ideal new bone formation was observed in Group A2 and D2. The results suggested that gene therapy using rhRunx2-modified ADSCs promoted new bone formation during osteoporotic mandibular DO and effectively compensated for the detrimental effects of systemic osteoporosis on new bone formation.

Effects of remifemin treatment on bone integrity and remodeling in rats with ovariectomy-induced osteoporosis

This study aims to evaluate the effects of Remifemin (isopropanolic extract of Cimicifuga Racemosa) on postmenopausal osteoporosis. 120 female Sprague-Dawley rats were randomly assigned to four groups: sham surgery with vehicle, ovariectomy with vehicle, ovariectomy with estradiol valerate, or ovariectomy with Remifemin. Daily oral administrations of the vehicle, estradiol valerate, or Remifemin began 2 weeks after surgery and lasted to 4, 8, or 12 weeks. Ten rats in each group were sacrificed at each timestep with assessment of bone mineral density, trabecular bone structure, and biomechanical parameters of the femur and lumbar vertebra. Bone turnover markers were evaluated 12 weeks after surgery. Both drugs prevented bone density loss in the distal end of the femur and preserved the trabecular bone structure in both the lumbar vertebra and distal end of the femur following ovariectomy. Both drugs protected bone stiffness at the tested regions and reduced bone reabsorption in ovariectomized rats. The preventive effects of Remifemin against bone-loss can rival those of estradiol valerate if treatment duration is adequately extended. In conclusion, Remifemin may demonstrate equivalent effects to estradiol valerate in terms of preventing postmenopausal osteoporosis.

The effect of bone morphometric changes on orthodontic tooth movement in an osteoporotic animal model

Objective:

To elucidate the effect of bone morphometric changes on orthodontic tooth movement (OTM) in zoledronic acid–treated ovariectomized rats.

Materials and Methods:

Twenty-one 10-week-old female Wistar rats were divided into ovariectomy (OVX), OVX with zoledronic acid administration (OVX + ZOL), and sham operation (control) groups. Two weeks after OVX, ZOL administration was initiated. Twelve weeks after OVX, a nickel-titanium closed-coil spring of 25-g force was applied mesially to the maxillary left first molar. In vivo micro–computed tomography (CT) of the left proximal tibia was performed for bone morphometric analysis every 2 weeks after OVX. In addition, OTM was investigated using micro-CT at 0, 12, and 14 weeks after OVX.

Results:

There were significant differences in the bone mineral content (BMC), bone volume (BV), BMC to tissue volume ratio (BMC/TV), and BV to TV ratio of trabecular bone between the control and OVX groups and also between the OVX + ZOL and OVX groups. In the OVX + ZOL group, increased BMC and BV in the cortical bone and increased bone mineral density (BMD) in the trabecular bone were observed. Interestingly, OTM in the OVX group was almost two times more than that in the control and OVX + ZOL groups. Moreover, OTM was correlated with BMD, BMC, BV, and BMC/TV in the trabecular bone.

Conclusions:

OVX accelerated OTM, while ZOL suppressed it. OTM demonstrated a significant negative relationship with trabecular bone mass.

Strontium fructose 1,6-diphosphate prevents bone loss in a rat model of postmenopausal osteoporosis via the OPG/RANKL/RANK pathway

AIM

To evaluate the protective effects of strontium fructose 1,6-diphosphate (FDP-Sr), a novel strontium salt that combined fructose 1,6-diphosphate (FDP) with strontium, on bone in an ovariectomy-induced model of bone loss.

METHODS

Eighty female Sprague-Dawley rats were ovariectomized (OVX) or sham-operated. Three months later, the rats were assigned to six groups (10 for each): sham-operated, OVX control, OVX+FDP-Sr (110, 220, or 440 mg/kg), or OVX+strontium ranelate (SR, 180 mg/kg). Drugs were administered orally for 3 months. When the treatment was terminated, the following parameters were assessed: bone mineral density (BMD), the biomechanical properties of the femur and lumbar vertebrae, trabecular histomorphology, serum phosphorus, calcium, bone-specific alkaline phosphatase (B-ALP), tartrate-resistant acid phosphatase 5b (TRACP5b), N-telopeptide of type I collagen (NTx) and a series of markers for oxidative stress. Receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG) levels in serum were measured using ELISA and their gene expression levels in the bone were measured using R-T PCR.

RESULTS

Treatment with FDP-Sr (220 or 440 mg/kg) or SR (180 mg/kg) significantly increased the BMD and improved the bone microarchitecture and bone strength in OVX rats. The treatments also decreased in the levels of H(2)O(2) and MDA, restored the CAT level in serum and bone marrow, increased the serum B-ALP and decreased NTx and TRACP 5b in OVX rats. Treatment with FDP-Sr decreased the RANKL level, and increased the OPG level in serum in a dose-dependent manner. It also significantly down-regulated the RANKL expression and up-regulated OPG expression in bone marrow.

CONCLUSION

FDP-Sr may be an effectve treatment for postmenopausal osteoporosis that acts, in part, via a decrease in osteoclastogenesis through the OPG\RANKL\RANK pathway.

Bone measurements by peripheral quantitative computed tomography in rodents

This chapter provides information for the use of peripheral quantitative computed tomography in small animals, including suggestions for study design, instrument setting, and data interpretation.

Simvastatin induces estrogen receptor-alpha expression in bone, restores bone loss, and decreases ERα expression and uterine wet weight in ovariectomized rats

We previously reported that simvastatin induces estrogen receptor-alpha (ERα) in murine bone marrow stromal cells in vitro. In this study, we investigated the effect of simvastatin on ERα expression in bone and uterus in ovariectomized (OVX) rats and evaluated bone mass, bone strength, and uterine wet weight. Three-month-old Sprague-Dawley female rats received OVX or sham operation. Six weeks later, the rats were treated orally with simvastatin (5 or 10 mg/kg/day), or intraperitoneally with 17-β-estradiol (E(2)) or a combination of simvastatin and E(2) for 6 weeks. Uterine wet weight, bone mineral density (BMD) of lumbar vertebrae, biomechanics of lumbar vertebrae, and induction of ERα expression in the bone and uterus were analyzed. The 6-week simvastatin treatment improved lumbar vertebral BMD and boosted biomechanical performance of the vertebral body compared to the OVX control, suggesting that simvastatin can treat osteoporosis caused by estrogen deficiency. More interestingly, simvastatin could increase ERα expression and synergy with estradiol in bone while antagonizing estradiol in the uterus, along with uterus atrophy and uterine wet weight decreases. In conclusion, these data suggest that simvastatin exert opposing modulatory effects on ERα expression on bone and uterus in ovariectomized rats, inducing ERα expression and synergy with estrogen to perform anabolic effects on the bones while decreasing E2 efficacy and uterine wet weight. This finding may be helpful to explain the mechanism of statin treatment in osteoporosis caused by estrogen deficiency.

The effect of SLActive surface in guided bone formation in osteoporotic-like conditions

OBJECTIVES

The aim of the study was to evaluate new bone formation under etched titanium (SLA) and modified-etched hydrophilic titanium (modSLA) domes placed on the calvarium of healthy, osteoporotic and osteoporotic treated with bisphosphonates rabbits.

METHODS

Experimental osteoporosis was induced by ovariectomy (OV) and calcium-deficient diet in 24 New Zealand female rabbits. Twelve OV rabbits were treated with weekly dozes of alendronate (Fosamax(®)) (B) while 12 OV rabbits received no treatment (O). Another 12 rabbits were sham operated and used as healthy controls (C). At 6 weeks following OV, one modSLA and one SLA titanium dome were placed in the parietal bones of each rabbit. The animals were sacrificed at 30 and 120 days following the dome placement. Various histomorphometric measurements were performed in the most central of the undecalcified sections produced.

RESULTS

After 30 days of healing, in the C group, the total bone (TB) area was 37.6% and 37.0% under the modSLA and SLA domes, respectively. In the O group, the TB was 35.7% and 24.8%. In the B group, TB was 37.0% and 32.1%, respectively. After 120 days of healing, in the C group TB was 40.1% and 36.4%, respectively. In the O group, TB was 29.6% and 27.9%, respectively. In the B group, TB was 49.7% and 42.5%, respectively. Hierarchical analysis of variance showed that the type of titanium dome significantly influenced new bone and the amount of new bone being in contact with inner surface of the dome (BIC) independently of the observation period and group (P<0.05). The administration of bisphosphonates influenced the BIC (P<0.05).

CONCLUSION

The use of modSLA surface may promote bone healing and osseointegration in osteoporotic rabbits, whereas administration of bisphosphonates may compromise the osseointegration of the newly formed bone at the early healing period.

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.

Comparison of the therapeutic effects of yeast-incorporated gallium with those of inorganic gallium on ovariectomized osteopenic rats

The purpose of this study was to compare the effect and toxicity of yeast-incorporated gallium (YG) with inorganic gallium (gallium nitrate, IG) in preventing osteoporosis in ovariectomized (OVX) Wistar female rats. After the rats were treated orally with YG and IG respectively, the urine calcium, plasma calcium, plasma phosphorus, bone mineral content, mechanical testing, and the mass of uterus, thymus, and body were examined. Treatments were performed over an 8-week period. Both YG and IG have a positive effect on mechanical strength and mineral content of OVX osteopenic rats. However, treatment with YG only caused a 24.3% and 41.4% decrease in plasma calcium and inorganic phosphate concentrations, whereas IG decreased plasma calcium and inorganic phosphate concentrations by up to 39.9% and 49.0%, respectively. It was different significantly. At the same time, YG significantly increased weights of atrophic uteri, weights of body, and also decreased the thymus mass in OVX animals, while IG did not exhibit any such effects. Our experiments have demonstrated that YG may reduce gallium-associated toxicity, hypocalcemia, and maintain its effect, while IG maintains both of its effect on osteoporosis and side effect of hypocalcemia.

Thalidomide affects the skeletal system of ovariectomized rats

Apart from having written an inglorious chapter in the history of medicine, thalidomide is currently being intensely studied because of its multidimensional activity. The aim of this study was to examine the effects of thalidomide on the skeletal system in ovariectomized and non-ovariectomized rats. The experiments were carried out with female Wistar rats, divided into eight groups: sham-operated control rats; sham-operated rats receiving thalidomide at doses of 15, 30 or 60 mg/kg, po; ovariectomized control rats; ovariectomized rats receiving thalidomide at doses of 15, 30 or 60 mg/kg, po. The drug was administered for 4 weeks. Body mass gain and the mass of the uterus, liver, spleen and thymus were studied. Macrometric parameters and content of mineral substances, calcium and phosphorus in the femur, tibia and L-4 vertebra and histomorphometric parameters of the femur and tibia were examined. In the femur, the mechanical properties of the whole bone and of the femoral neck were examined. Thalidomide did not affect the skeletal system of the non-ovariectomized rats. Bilateral ovariectomy induced osteoporotic skeletal changes in mature female rats. The effects of thalidomide on the skeletal system of ovariectomized rats depended on the dose used. With a dose of 15 mg/kg, po, thalidomide counteracted some osteoporotic changes induced by estrogen deficiency. With a dose of 60 mg/kg, po, thalidomide intensified the destructive effects of estrogen deficiency on the rat skeletal system.

Strontium ranelate improves bone strength in ovariectomized rat by positively influencing bone resistance determinants

SUMMARY

Treatment of adult ovariectomized (OVX) rats with strontium ranelate prevented vertebral biomechanics degradation as a result of the prevention of bone loss and micro-architecture deterioration associated to an effect on intrinsic bone material quality. Strontium ranelate influenced the determinants of bone strength by prevention of ovariectomy-induced changes which contribute to explain strontium ranelate antifracture efficacy.

INTRODUCTION

Strontium ranelate effects on the determinants of bone strength in OVX rats were evaluated.

METHODS

Adult female Sprague-Dawley rats were OVX, then treated daily for 52 weeks with 125, 250, or 625 mg strontium ranelate/kg. Bone strength, mass, micro-architecture, turnover, and intrinsic quality were assessed.

RESULTS

Strontium ranelate prevented ovariectomy-induced deterioration in mechanical properties with energy necessary for fracture completely maintained vs. SHAM at 625 mg/kg/day, which corresponds to the clinical dose. This was related to a dose-dependent effect on bone volume, higher trabeculae number, and lower trabecular separation in strontium ranelate vs. OVX. Load and energy required to induce lamella deformation were higher with strontium ranelate than in OVX and in SHAM, indicating that the bone formed with strontium ranelate is able to withstand greater damage before fracture. Bone formation was maintained high or even increased in strontium ranelate as shown by mineralizing surfaces and alkaline phosphatase while strontium ranelate led to reductions in deoxypyridinoline.

CONCLUSION

Strontium ranelate administered at 625 mg/kg/day for 52 weeks prevented OVX-induced biomechanical properties deterioration by influencing the determinants of bone strength: it prevented bone loss and micro-architecture degradation in association with an effect on intrinsic bone quality. These beneficial effects on bone contribute to explain strontium ranelate antifracture efficacy.

Diet calcium level but not calcium supplement particle size affects bone density and mechanical properties in ovariectomized rats

Calcium (Ca) supplements, especially Ca carbonate (CaCO3), are the main alternative sources of dietary Ca and an important part of a treatment regimen for osteoporosis, the most common metabolic bone disorder of aging and menopause. In a female ovariectomized (OVX) rat model for studying postmenopausal osteoporosis, we tested the hypothesis that a small compared with a large particle size of CaCO3 (13.0- vs. 18.5-mum geometric diameter) would result in increased Ca balance and subsequently bone mass and that this would be affected by dietary Ca level. We used 6-mo-old rats that were OVX either at 6 or 3 mo of age as models of early or stable menopausal status, respectively. The rats received semipurified diets that contained either 0.4 or 0.2% dietary Ca provided from CaCO3 of 2 particle sizes. A group of Sham-operated rats with intact ovaries served as control and were fed 0.4% dietary Ca from large particles. Estrogen deficiency as a result of ovariectomy had an adverse effect on bone density, mineral content, and bone mechanical properties (P < 0.001). Reducing dietary Ca from 0.4 to 0.2% resulted in significant adverse effects on bone density and mechanical properties (P < 0.001). The particle size of CaCO3 did not affect total Ca balance, bone dual energy X-ray absorptiometry and peripheral quantitative computed tomography indices, bone ash and Ca content, or the mechanical determinants of bone strength. We conclude that a decrease in particle size of CaCO3 to 70% of that typically found in Ca supplements does not provide a benefit to overall Ca metabolism or bone characteristics and that the amount of Ca consumed is of greater influence in enhancing Ca nutrition and skeletal strength.

Simvastatin increases osteoblasts and osteogenic proteins in ovariectomized rats

BACKGROUND

Previous reports have indicated that statins could prevent bone loss in ovariectomized (OVX) rats and increase the expressions of osteogenic genes in cultured osteoblasts. In this study, we hypothesized that simvastatin might increase osteoblast number and protein expressions of osteogenic markers localized in bones in concomitance with the prevention of bone loss in OVX rats.

MATERIALS AND METHODS

Fifty-four 3-month-old OVX and sham-operated (SHAM) female Sprague-Dawley rats were used. Simvastatin (10-20 mg kg(-1) day(-1)) was administrated orally for 6 weeks. Trabecular volume, osteoblast number and osteogenic proteins including BMP2, collagen type I and osteocalcin on bone sections obtained from lumbar vertebral body, distal femur and proximal tibia were measured.

RESULTS

The results showed that SHAM rats had significantly less trabecular bone volume and osteoblast number than that of OVX rats 6 weeks after operation. Oral simvastatin treatment (10-20 mg kg(-1) day(-1)) increased bone volume and osteoblast number in the distal femurs, proximal tibiae and vertebrae of OVX rats. Furthermore, the osteoblastic cells with immuno-stained BMP2, collagen type I and osteocalcin in vertebral bones were significantly increased by simvastatin treatment (20 mg kg(-1) day(-1)) in OVX rats.

CONCLUSIONS

This study demonstrates that simvastatin enhances the production of osteogenic proteins in bone and this effect may contribute to the prevention of bone loss in OVX rats.

Comparing the effects of atamestane, toremifene and tamoxifen alone and in combination, on bone, serum lipids and uterus in ovariectomized rats

Complete estrogen blockade remains under investigation as a means to optimize anti-estrogen therapy in breast cancer thus both the efficacy and end-organ toxicities are of interest with combinations. We hypothesized that a steroidal aromatase inhibitor (AI) atamestane (ATA) alone, and in combination with the anti-estrogens tamoxifen (TAM) or toremifene (TOR) would have beneficial effects in ovariectomized (OVX) rats on key end-organ functions including bone and lipid metabolism and on the endometrium. Significant positive effects on bone were noted with ATA, TOR, TAM, ATA+TOR, or ATA+TAM. TOR, TAM, ATA+TOR, or ATA+TAM caused significant decreases in serum cholesterol and low-density lipoprotein cholesterol whereas ATA had no effect. Uterine weight and epithelium lining height were not increased by ATA but were by TOR and TAM. No significant differences were found in the key parameters outlined above between OVX rats given TOR and ATA+TOR, or TAM and ATA+TAM. Our data show that ATA in combination with TOR or TAM is equivalent to TOR or TAM alone in terms of end-organ effects within a range of clinically relevant doses. Further studies of combinations of AIs with anti-estrogens on end-organ function are merited.

Correlation among geometric, densitometric, and mechanical properties in mandible and femur of osteoporotic rats

We have previously demonstrated bone loss of the mandible and femur in experimental osteoporotic rats and its prevention by medication, using peripheral quantitative computed tomography (pQCT). In the present study, the mechanical properties of the mandible and femur and the correlation to their geometric and densitometric properties were studied in ovariectomized rats with or without etidronate treatment. Fifty-four Wistar strain SPF female rats, 26 weeks old, were randomly assigned to four groups: (1) Basal group (12 rats, 1.0% Ca diet); (2) Sham group (Sham-operated, 12 rats, 0.1% Ca diet); (3) OVX group (ovariectomized, 15 rats, 0.1% Ca diet); (4) Treated group (OVX + etidronate, 15 rats, 0.1% Ca diet). Total bone mineral density (BMD), cortical BMD, cross-sectional cortical bone area, cross-sectional cortical bone thickness, crosssectional moment of inertia (CSMI), and polar strength index (SSI) of the mandible and femur were measured by pQCT. The failure load of mandible and femur was evaluated by three-point bending. The failure load of both bones was significantly lower in the Sham group compared with the Basal group. The OVX group further had a 8% and 7% decrease in the failure load for mandible and femur, respectively, compared to the Sham group. Treatment with etidronate led to an increase in the failure load compared with the OVX group. The failure load was related to the pQCT-assessed variables, especially with cortical bone area and total BMD. Moreover, the geometric and densitometric properties and failure load in the mandible showed a correlation to those in the femur.

Effects of estrogen deficiency on tooth movement after force application: an experimental study in ovariectomized rats

OBJECTIVE

The aim of this study was to investigate the effects of estrogen deficiency on tooth movement in ovariectomized rats.

MATERIAL AND METHODS

Forty-two adult female Sprague-Dawley rats were assigned at random to one of the following groups: test group (n=20), ovariectomized rats (or estrogen-deficient rats); control group (n=22), non-ovariectomized rats. Two months after ovariectomy, expansion springs exerting 10 g of force were inserted between the upper central incisors in both groups. The amount of movement was measured daily until tooth movement began and then at intervals of 3 days. The rats were sacrificed 18 days after applying the expansion spring and histomorphometric analysis was performed along the left upper central incisor root towards the apex of the alveolar bone.

RESULTS

The amount and speed of movement was observed to be greater in ovariectomized rats. On histomorphometric analysis, osteoblast and osteocyte counts on the pressure side were higher in the non-ovariectomized group than in the ovariectomized group (p<0.001). In contrast, the osteoclast count was significantly higher (p<0.01) in the ovariectomized group than in the non-ovariectomized group. The osteoblast and osteocyte counts were significantly higher (p<0.001) on tension side in the non-ovariectomized group than in the ovariectomized group.

CONCLUSION

Estrogen deficiency increased orthodontic tooth movements but counts of osteoblasts, which are responsible for new bone formation, were lower in regions of tension and of pressure.

Ovariectomy of 12-month-old rats: effects on osteoprogenitor numbers in bone cell populations isolated from femur and on histomorphometric parameters of bone turnover in corresponding tibia

Ovariectomy (OVX) in rats results in increased bone turnover and decreased bone volume and bone mineral density when measured in the metaphyses of long bones. We have investigated the effects of OVX on changes in the number of progenitors in cell populations derived from the metaphyseal bone of femurs of ovariectomized rats at 12 months of age, by using colony assays, bone nodule assays, and limiting dilution analysis at 1.5 and 9 months post-OVX. We have also measured histomorphometric parameters of bone formation and resorption in the corresponding tibia at the same time-points. A significant increase, as shown by bone nodule assays and limiting dilution analysis, occurs in the number of progesterone- and dexamethasone-responsive osteoprogenitors in cell populations isolated from ovariectomized rats at the 9-month post-OVX time-point. Progesterone-responsive osteoprogenitors are also increased at 1.5 months post-OVX. The number of fibroblast colony-forming units does not change. Histomorphometry has shown that OVX causes an increase in osteoblast surfaces, mineralizing surfaces, and bone formation rate at both 1.5 and 9 months post-OVX. The mineral apposition rate is increased at 1.5 months post-OVX. OVX also increases parameters of bone resorption at both time-points, the net result being a decrease in bone mineral density and cancellous bone volume at 9 months post-OVX. Thus, OVX in rats at 12 months of age is associated with an increase in the number of both progesterone- and dexamethasone-responsive osteoprogenitors 9 months post-OVX; this corresponds with increases in the histomorphometric parameters of bone formation.

High-calcium diet modulates effects of long-term prolactin exposure on the cortical bone calcium content in ovariectomized rats

High physiological prolactin induced positive calcium balance by stimulating intestinal calcium absorption, reducing renal calcium excretion, and increasing bone calcium deposition in female rats. Although prolactin-induced increase in trabecular bone calcium deposition was absent after ovariectomy, its effects on cortical bones were still controversial. The present investigation, therefore, aimed to study the effect of in vivo long-term high physiological prolactin induced by either anterior pituitary (AP) transplantation or 2.5 mg/kg prolactin injection on cortical bones in ovariectomized rats. Since the presence of prolactin receptors (PRLR) in different bones of normal adult rats has not been reported, we first determined mRNA expression of both short- and long-form PRLRs at the cortical sites (tibia and femur) and trabecular sites (calvaria and vertebrae) by using the RT-PCR. Our results showed the mRNA expression of both PRLR isoforms with predominant long form at all sites. However, high prolactin levels induced by AP transplantation in normal rats did not have any effect on the femoral bone mineral density or bone mineral content. By using (45)Ca kinetic study, 2.5 mg/kg prolactin did not alter bone formation, bone resorption, calcium deposition, and total calcium content in tibia and femur of adult ovariectomized rats. AP transplantation also had no effect on the cortical total calcium content in adult ovariectomized rats. Because previous work showed that the effects of prolactin were age dependent and could be modulated by high-calcium diet, interactions between prolactin and these two parameters were investigated. The results demonstrated that 2.0% wt/wt high-calcium diet significantly increased the tibial total calcium content in 9-wk-old young AP-grafted ovariectomized rats but decreased the tibial total calcium content in 22-wk-old adult rats. As for the vertebrae, the total calcium contents in both young and adult rats were not changed by high-calcium diet. The present results thus indicated that the adult cortical bones were potentially direct targets of prolactin. Moreover, the effects of high physiological prolactin on cortical bones were age dependent and were observed only under the modulation of high-calcium diet condition.

The effects of atamestane and toremifene alone and in combination compared with letrozole on bone, serum lipids and the uterus in an ovariectomized rat model

We compared the effects of atamestane (ATA) and toremifene (TOR) alone and in combination, with letrozole (LET) on bone, serum lipids and the uterus in ovariectomized (OVX) rats after 16 weeks of treatment. Compared to OVX controls lumbar vertebral and femoral BMD as well as mechanical strength and trabecular bone volume were significantly greater in animals given ATA, TOR or ATA + TOR. The effects of ATA were not reversed by the androgen receptor blocker, flutamide (FLT). Serum cholesterol, low-density lipoprotein cholesterol and triglycerides were reduced by TOR and ATA + TOR whereas they remained unchanged in animals receiving ATA, ATA + FLT, and LET. The uterine epithelium in OVX animals was equally stimulated by TOR and ATA + TOR and unaffected by ATA or LET. Intact animals had significant atrophy of the uterine epithelium when receiving ATA. In summary, TOR alone or in combination with ATA had a predictable stimulatory effect on bone and the uterine epithelium while reducing key parameters of lipid metabolism. In contrast, ATA but not LET had an unexpected stimulatory effect on the OVX rat's bone and this was not reversed by the anti-androgen FLT leaving this finding unexplained for now. ATA is distinct from LET on end-organ function and this favorable profile makes clinical testing of this steroidal aromatase inhibitor of interest in the clinical setting.

Bone loss dynamics result in trabecular alignment in aging and ovariectomized rats

Because of the destructive nature of techniques used to measure bone morphometry, studies of architectural changes and bone loss have utilized cross-sectional study designs, with all its inherent limitations in nuances. Here, the results of a longitudinal study using in vivo micro-CT are presented elucidating the dynamics of bone loss and architectural adaptation in rat models of aging and postmenopausal bone loss. Using 3-D methodology, we observed the changes in bone architecture in the proximal tibia of normally aging and ovariectomized rats for 54 weeks. Spatial patterns in bone resorption were observed that were similar for both groups. Remaining trabeculae increased in thickness or were remodeled into new trabecular structures, especially in the ovariectomized animals. The combination of bone loss and bone formation resulted in alignment of trabeculae across the growth plate. Cortical modeling that was associated with growth continued after cessation of longitudinal growth in the ovariectomized animals, resulting in shape changes of the proximal tibia. The organized nature of the changes in bone architecture that occurred after ovariectomy and the high similarity with the changes observed in the normally aging animals, suggest that estrogen depletion resulted in an acceleration of a normal bone adaptation process. The observed aligning of trabeculae suggests regulation through mechanical loading.

Effect of treadmill exercise on bone mass in female rats

Increasing peak bone mass at skeletal maturity, minimizing bone loss during middle age and after menopause, and increasing bone mass and preventing falls in advanced age are important measures for preventing osteoporotic fractures in women. Exercise has generally been considered to have a positive influence on bone health. This paper reviews the effects of treadmill exercise on bone in young, adult, ovariectomized, and osteopenic female rats. Treadmill exercise increases cortical and cancellous bone mass of the tibia as a result of increased bone formation and decreased bone resorption in young and adult rats. The increase in lumbar bone mass seems to be more significant when long-term exercise is applied. Treadmill exercise prevents cancellous bone loss at the tibia as a result of suppressed bone resorption in ovariectomized rats, and increases bone mass of the tibia and mechanical strength of the femur, as a result of suppressed bone resorption and increased bone formation in osteopenic rats after ovariectomy. Treadmill exercise transiently decreases the serum calcium level as a result of accumulation of calcium in bone, resulting in an increase in serum 1,25-dihydroxyvitamin D(3) level and a decrease in serum parathyroid hormone level. We conclude that treadmill exercise may be useful to increase bone mass in young and adult rats, prevent bone loss in ovariectomized rats, and increase bone mass and bone strength in osteopenic rats, especially in the long bones at weight-bearing sites. Treadmill exercise may have a positive effect on the skeleton in young, and adult, ovariectomized, and osteopenic female rats.

The selective estrogen receptor modulator SCH 57068 prevents bone loss, reduces serum cholesterol and blocks estrogen-induced uterine hypertrophy in ovariectomized rats

Our objective was to determine the effects of SCH 57068 alone and with 17 beta-estradiol (E(2)) on bone, lipids and uteri in ovariectomized (OVX) rats. In OVX animals lumbar vertebral and femoral bone mineral density (BMD) were significantly higher after 12 weeks of treatment with SCH 57068 than in untreated OVX controls. Similarly BMD was superior in OVX + E(2) + SCH 57068 treated animals than in OVX + E(2) controls. SCH 57068 also significantly reduced the increase in bone turnover markers, serum pyridinoline and serum osteocalcin levels, induced by OVX, and increased mechanical bone strength. SCH 57068 also significantly reduced the rise in serum cholesterol and low-density lipoprotein cholesterol induced by OVX. SCH 57068 had no stimulatory effect on uterine epithelium when given alone in OVX rats. SCH 57068 (1 and 2.5 mg/kg) reduced uterine weight and blocked endometrial stimulation induced by E(2). In summary, SCH 57068 adds to the positive effects of E(2) on bone and lipid metabolism but blocks the stimulatory effects of E(2) on the uterus. Potentially, E(2) + SCH 57068 could be combined for the treatment and prevention of breast cancer or as a novel hormone replacement therapy.

Effect of ovariectomy on dexamethasone- and progesterone-dependent osteoprogenitors in vertebral and femoral rat bone cell populations

We have found previously that the skeleton of adult female rats contains dexamethasone (Dex)- and progesterone (Prog)-dependent osteoprogenitors, and that estrogen treatment in vitro upregulates proliferation and differentiation of the Prog-dependent but not of the Dex-dependent osteoprogenitors (Bone 1997;20:17-25). The purpose of the present study was to determine whether ovariectomy (OVX) would have different effects on these two classes of osteoprogenitors. Six-month-old Sprague-Dawley rats underwent OVX and the lumbar vertebrae and proximal femurs were collected 1.5, 3, and 6 months after OVX. Cells were obtained from outgrowths of explant cultures and grown in alpha-MEM with 10% FBS, 50 microg/ml ascorbic acid, and 5 mM beta-glycerophosphate. Osteoprogenitors were identified by their ability to generate a colony of osteoblastic cells forming bone (bone nodule). We also evaluated the number of colony-forming units-fibroblast (CFU-F) and of alkaline phosphatase (AP)-positive CFU-F. In cell populations obtained from vertebrae of rats ovariectomized for 1.5, 3, and 6 months and their corresponding control rats, both Dex (1-100 nM) and Prog (1-10 microM) dose-dependently stimulated nodule formation. Both Dex- and Prog-induced nodule formation were higher in cell populations from control rats than in those from ovariectomized rats (P < 0.001). Numbers of CFU-F and AP-positive CFU-F were also higher in cell populations from control rats compared with those from ovariectomized rats. Estrogen (10 nM) enhanced Prog-dependent bone nodule formation but decreased Dex-dependent bone nodule formation in populations from both control and ovariectomized rats. In femoral populations, the responses to Dex (10 nM), Prog (3 microM), and estrogen (10 nM) were similar to those of the vertebral populations in both control and ovariectomized rats. Our results demonstrate that ovariectomy in rats results in a dramatic decrease in the number of both Dex- and Prog-dependent osteoprogenitors in cell populations from vertebrae and proximal femurs. In addition, we confirmed our previous observation that estrogen upregulated proliferation and differentiation of Prog-dependent progenitors, but found here that estrogen clearly downregulated proliferation and differentiation of the Dex-dependent progenitors.

Osteoblasts cultured from osteoporotic bone: a comparative investigation on human and animal-derived cells

In vitro studies on pathophysiology and innovative treatments of many orthopaedic diseases, based on the investigations of cells from pathologic skeletal tissues, greatly improve basic knowledge of osteoporosis. Primary osteoblast (OB) cultures derived from osteopenic bone from different species (human, rat, sheep) were compared to assess the differences that should be taken into account when performing in vitro biocompatibiliy tests or investigating pharmacological and physical treatments. Primary OB were isolated from osteopenic patients and animals by well-established methods and their metabolism was assessed with or without 1,25(OH)2D3. The greatest significant differences were observed between rat and human cells both under basal conditions and after 1,25(OH)2D3 stimulation. In addition, the response to 1,25(OH)2D3 stimulation of OBs from osteopenic rats was significantly different from that of human and sheep OB cultures, in terms of NO, OC, IL-6, and TGF-beta1. Cells derived from osteopenic sheep behaved much more similarly to those from humans, except for a significant difference in terms of TGF-beta1 observed both under basal conditions and after stimulation.

Melatonin increases oestradiol-induced bone formation in ovariectomized rats

To assess the effect of melatonin on bone metabolism in ovariectomized rats, receiving oestradiol therapy or not, melatonin was administered in the drinking water (25 microg/mL water) and oestradiol (10 microg/kg body weight) or vehicle was given subcutaneously 5 days/week for up to 60 days after surgery. Urinary deoxypyridinoline (a marker of bone resorption) and circulating levels of bone alkaline phosphatase activity (a marker of bone formation), as well as serum calcium and phosphorus levels, were measured every 15 days. Bone area (BA), bone mineral content (BMC), bone mineral density (BMD) and total body fat (expressed as 100 g body weight) were measured by dual-energy X-ray absorptiometry at the end of the experiment. Body weight and total body fat were augmented after ovariectomy, and decreased after melatonin or oestradiol treatment. The effect of melatonin on body weight was seen in sham-operated rats only. Ovariectomy augmented, and melatonin or oestradiol lowered, urinary deoxypyridinoline excretion. This effect of melatonin and oestradiol was seen mainly in ovariectomized rats. The efficacy of oestradiol to counteract ovariectomy-induced bone resorption was increased by melatonin. Melatonin or oestradiol lowered serum bone alkaline phosphatase activity. Melatonin inhibition was seen mainly on the increase of bone alkaline phosphatase activity that followed ovariectomy. Serum phosphorus levels decreased after melatonin administration and were augmented after oestradiol injection; overall, melatonin impaired the increase of serum phosphorus caused by oestradiol. Ovariectomy decreased, and oestradiol increased, serum calcium levels while melatonin augmented serum calcium in sham-operated rats only. On day 60 after surgery, BMD and content decreased after ovariectomy and were increased after oestradiol injection. Melatonin augmented BA of spine and BMC of whole of the skeleton and tibia. The highest values observed were those of rats treated concurrently with oestradiol and melatonin. The present results indicate that: (i) melatonin treatment restrained bone remodelling after ovariectomy; (ii) the effect of melatonin required adequate concentrations of oestradiol; (iii) melatonin augmented oestradiol effects on bone in ovariectomized rats; (iv) a counter-regulation by melatonin of the increase in body fat caused by ovariectomy was uncovered. The melatonin doses employed were pharmacological in terms of circulating melatonin levels but not necessarily for some other fluids or tissues.

Time course of epiphyseal growth plate fusion in rat tibiae

Although the rat is the most common animal model used in studying osteoporosis, it is often used inappropriately. Osteoporosis is a disease that most commonly occurs in humans long after growth plate fusion with the associated cessation of longitudinal bone growth, but there has been a question as to when or to what extent the rat growth plate fuses. To investigate this question, we used microcomputed X-ray tomography, at voxel resolutions ranging from (5.7 micro m)(3) to (11 micro m)(3), to image the proximal epiphyseal growth plates of both male (n = 19) and female (n = 15) rat tibiae, ranging in age from 2 to 25 months. The three-dimensional images were used to evaluate fusion of the epiphyseal growth plate by quantitating the amount of cancellous bone that has bridged across the growth plate. The results suggest that the time course of fusion of the epiphyseal growth plate follows a sigmoidal pattern, with 10% of the maximum number of bridges having formed by 3.9 months in the male tibiae and 5.8 months in the female tibiae, 50% of the maximum number of bridges having formed by 5.6 months in the male tibiae and 5.9 months in the female tibiae, and 90% of the total maximum of bridges have formed by 7.4 months for the males and 6.5 months for the females. The total volume of bridges per tibia at the age at which the maximum number of bridges per tibia has first formed is 0.99 mm(3)/tibia for the males and 0.40 mm(3)/tibia for the females. After the maximum number of bridges (-290 for females, -360 for males) have formed the total volume of bridges per tibia continues to increase for an additional 7.0 months in the males and 17.0 months for the females until they reach maximum values (-1.5 mm(3)/tibia for the males and -2.2 mm(3)/tibia for the females).

Comparison of osteopenia after gastrectomy, ovariectomy and prednisolone treatment in the young female rat

Rat models of osteopenia include ovariectomy and long-term glucocorticoid treatment. Although ovariectomy produces significant trabecular bone loss after 2 weeks, long-term glucocorticoid treatment has been reported to cause osteopenia in some studies but not in others. In the present 8-week-study, we compared the osteopenia associated with gastrectomy (GX) to that induced by ovariectomy (OVX) or prednisolone (PRE) treatment. Female Sprague-Dawley rats (10 weeks old) were subjected to GX, OVX, PRE treatment or SHAM operation. At the end of the study, calvariae, femurs and fifth lumbar vertebrae (L5) were collected and subjected to bone density measurement (femur and L5), transillumination (calvaria) and histomorphometry (calvaria and femur). Bone density was reduced in L5 and the distal femur in the OVX and GX groups, but not in the PRE group. Transillumination of the calvaria showed marked bone loss in the GX rats, but not in the other groups. Morphometric analysis of the femur revealed reduced trabecular bone volume, trabecular thickness, trabecular number and osteoclast number, but increased osteoclast surface (expressed as per cent of the trabecular bone surface covered by osteoclasts) in the GX and OVX rats. The PRE rats seemed unaffected. Cortical thickness was reduced in the GX rats, but not in the other groups. The findings indicate that GX induces osteopenia in, e.g., femur and vertebra of a magnitude similar to or greater than that induced by OVX, while at the same time inducing osteopenia in the calvaria. Although osteoclast activation seems to contribute, the precise mechanism underlying the GX-evoked osteopenia remains obscure.