Bone Tissue In Ovariectomized Rats Research Articles

Ozone Improved Bone Dynamic of Female Rats Using Zoledronate.

The aim of this study was to analyze the effect of ozone (OZN) therapy on the dynamics of bone tissue in ovariectomized rats treated with zoledronic acid (ZOL). Female Wistar rats aged 6 months (n = 110) were subjected to bilateral ovariectomy (OVX). At month 3 post-OVX, 10 animals were euthanized to characterize the bone tissue architecture using microtomography (micro-CT). The remaining animals were divided into two groups: ZOL group, administered with ZOL (100 μg/kg body weight); saline (SAL) group (0.45 mL of SAL solution), both for 28 days. At month 3 post-treatment, 10 animals from each group were euthanized to characterize the bone architecture using micro-CT. The remaining animals were divided into the following groups: ZOL (n = 20), ZOL + OZN (n = 20); SAL (n = 20), and SAL + OZN (n = 20). The animals in ZOL + OZN and SAL + OZN groups were intraperitoneally administered with OZN (0.7 mg/kg body weight) once every 2 days. On days 30 and 60, six animals from each group were euthanized for analysis and structural characterization of bones in the femoral head and spine. Some samples of the femoral neck were subjected to biomechanical tests, while some samples were analyzed under a laser confocal microscope. The other samples collected from the femoral neck and spine were analyzed for area of neoformed bone and used for performing inflammatory cell and osteocyte counts. Data were submitted to statistical analysis considering a significance level of p < 0.05. Bone volume percentage and osteocyte and inflammatory cell counts were upregulated in the femoral head region of the ZOL + OZN group. Biomechanical analysis of the femoral neck revealed that the modulus of elasticity was similar between the ZOL and ZOL + OZN groups but differed significantly between the SAL and SAL + OZN groups. The positive areas for calcein and alizarin in the ZOL and ZOL + OZN groups were higher than those in the SAL and SAL + OZN groups. This suggested a positive synergistic effect of OZN and ZOL on the maintenance of bone mass and restoration of bone tissue vitality in ovariectomized rats.

High-salt diet accelerates bone loss accompanied by activation of ion channels related to kidney and bone tissue in ovariectomized rats.

Excessive salt intake can induce a variety of diseases, such as hypertension, cardiovascular disease, kidney disease and so on，it is also one of the factors promoting bone resorption. The mechanism of osteoporosis-induced exacerbations of high salt diet is not well-defined. In this study, we used ovariectomized 6-month-old Sprague Dawley rats to construct a high bone turnover model, and then administrated with high sodium chloride diet (2.0% w/w NaCl, 8.0% w/w NaCl) for 12 weeks to observe the effect of high salt diet on bone metabolism. The results showed that high salt diet could lead to the destruction of bone microstructure, promote the excretion of urinary calcium and phosphorus and accelerate the bone turnover, as well as cause the pathologic structural abnormalities in renal tubular. At the same time, it was accompanied by the up-regulated expression of the epithelial sodium channel (ENaCα), voltage-gated chloride channels (ClC)-3 and the down-regulated expression of Na-Cl cotransporter (NCC), sodium calcium exchanger (NCX1) in femoral tissue and renal tubules. These findings confirm that high salt diet can destroy the microstructure of bone by increasing bone resorption and affect some ion channels of bone tissue and renal tubule in ovariectomized rats.

Effect of escitalopram oxalate on quality bone tissue of ovariectomized rats

Effect of escitalopram oxalate on quality bone tissue of ovariectomized rats

Effects of Bushen Zhuanggu Granules on expressions of serum GH with IGF-1 and its receptors in bone tissue of ovariectomized rats

Objective: To investigate the effects of Bushen Zhuanggu granule on the expressions of serum growth hormone (GH) and insulin-like growth factor-1(IGF-1) and their receptors in bone tissues of ovariectomized rats. Methods: Forty-eight SD female rats (weight 273±21.3 g) were divided into 4 four groups: the dosage of Bushen Zhuanggu granule group (BSZG) was 2.5 g/(kg·d),the do -sage of estradiol group(E2) was 0.071mg/(kg·d),sham group (SHAM) and ovariectomized model group (OVX group) were given the same amount of saline by oral administration.Each group included 12 rats,the treatments were conducted once a day. After 3 and 6 months of treatment,bone mineral density (B -MD) was measured by bone density instrument;the serum levels of GH and IGF-1 were detected by EL-ISA;the expressions of GHR and IGF-1R of bone tissue were detected by qPCR;the optical density(OD)value and positive cell count of pituitary GH immunohistochemical tablets were analyzed by Image J software,respectively. Results: ①After 3 months intervention,compared with the SHAM, the BMD of the spine in E2 group was increased(P＜0.05),and the BMD of both parts in BSZG group were increased(P＜0.05).After two stage intervention,BMD of both part in the two drug groups was higher than that in the OVX group(P＜0.05).②After two-stage intervention,the expression levels of serum GH and IGF-1,GHR and IGF-1R in BSZG group were higher than those in OVX group (P＜0.05).The levels of serum GH and it's receptors in the E2 group were increased (P＜0.05), but the serum IGF-1 level remained unchanged (P＞0.05) or even was decreased (P＜0.05).③After two stage in -tervention,the OD values and the positive cells count in the two drug intervention groups were increased (P＞0.05).④Pearson correlation analysis showed that serum GH,IGF-1 concentration and it's receptors in bone tissue were positively related with BMD. Serum GH concentration was positively correlated with OD values and number of positive cells. Conclusion: Bushen Zhuanggu granule can be used to improve the expressions of GH,IGF-1 in serum and its receptors in bone tissues of ovariectomized osteoporosis rats to prevent further loss of bone mass and increase bone mineral density.

BIOCHEMICAL, HISTOPATHOLOGICAL AND IMMUNOHISTOCHEMICAL EVALUATION OF ALTERATIONS IN BLOOD AND TIBIAL BONE TISSUES OF OVARIECTOMIZED RATS IN THE ACUTE PHASE

AMAÇ: Menopoz sonrası meydana gelen osteoporoz, kemik kütlesinde azalma ve kemik dokunun yapısında bozulma ile sonuçlanır. Ovariektomi sonrası, osteoporoz bulgularına rastlanmakta ve kemik yıkımı kemik oluşumundan fazla olduğundan kemik kaybına neden olmaktadır. ADAMs transmembran proteinleri ekstrasellüler matriksin yeniden yapılandırılmasında ve embriyonik gelişim, hücre göçü, adezyon, anjiyogenez olmak üzere birçok fizyolojik süreçte rol alırlar. Çalışmamızın amacı, ovariektomi oluşturulan sıçanlarda kan ve kemik dokusunda akut dönemde meydana gelen değişikleri biyokimyasal, histopatolojik ve immünohistokimyasal yöntemlerle araştırmaktır.GEREÇ VE YÖNTEM: Sağlıklı ve dişi 20 adet erişkin Wistar albino sıçan kontrol (n:10) ve bilateral ovariektomi uygulanan grup (n:10) olmak üzere 2 gruba ayrıldı. Anestezi altında yumurtalık rahim boynu kısmından 2 cm'lik kesi yapılarak, iki dorsolateral insizyon ile uterus apeksinden çift taraflı yumurtalıklar ipek iplikle çıkarıldı. Ovariektomi den 1 hafta sonra, deney hayvanları feda edildi. Serum östrojen, kalsiyum ve alkalin fosfat değerlerini ölçmek için her hayvandan kan örnekleri alındı, tibia kemikleri çıkarılarak formalin çözeltisine alınarak tespit edildikten sonra, dekalsifiye etme işlemine tabi tutuldu ve rutin histolojik işlemlerin ardından parafin blokları hazırlandı, yarı-ince kesitleri alınarak histopatolojik incelemeler için Hematoksilen Eozin boyası ile boyandı. İmmünohistokimyasal analiz için, antijen retrival işlemini uygulamak üzere sitrat tamponuna alındıktan sonra hidrojen peroksit ile muamele edildi. Kesitlere anti-ADAMTS-1 primer antikoru uygulandı, ışık mikroskobunda değerlendirildi.BULGULAR: Kontrol grubunda radiyal tarzda dağılmış havers kanalları ve volkman kanalları izlenirken, kollajen lifler birbirine paralel ve düzenliydi. Ovariektomi grubunda ise kemik matriksinde dejeneratif değişiklikler, lamelli kemik yapısında bozulma izlendi. ADAMTS-1 ekspresyonu açısından, kontrol grubu osteoblast ve osteosit hücrelerinde ve kemik matriksindeki ince kollajen liflerde ekspresyon pozitifti. Ovariektomi grubunda, dejeneratif alanda yer alan osteoklast hücrelerinde ADAMTS-1 ekspresyonunda artış, osteon yapılarında, endotel hücrelerinde ADAMTS-1 pozitif ekspresyonu izlendi. Kanda östrojen değerleri açısından, ovariektomi grubunda kontrol grubuna göre anlamlı bir düşüş gözlendi. Kalsiyum değerlerinde ise kontrol ve ovariektomi gruplarının değerleri birbirine yakındı. Alkalen fosfataz değerlerinin ovariektomi grubunda yükseldiği görüldü(p=0,01).SONUÇ: Çalışmamız sonucu elde ettiğimiz veriler ışığında, osteoporoz tedavisine ADAMTS-1 proteinlerinin dahil edilmesinin yeni tedavi yöntemlerini destekleyebileceği düşüncesindeyiz.

Genistein and Silicon Synergistically Protects Against Ovariectomy-Induced Bone Loss Through Upregulating OPG/RANKL Ratio.

We have reported that genistein (Gen) and silicon (Si) have synergistic effects on ovariectomy-induced bone loss in rat; however, the potential mechanisms behind this effect were not fully clarified yet. This study was performed to evaluate the bone protective mechanisms of concomitant intake of genistein and silicon in ovariectomized rat by OPG/RANKL axis. Three-month-old Sprague-Dawley female rats were subjected to ovariectomy (OVX) or sham surgery; after surgery, the OVX rats were randomly divided into five groups: OVX-Gen, OVX-Si, OVX-Gen-Si, OVX-E, and OVX. Genistein, silicon, and 17β-estradiol supplementation were started after ovariectomy and continued for 10weeks. The results showed that genistein and silicon treatment increased the bone mineral density (BMD) of ovariectomized rats. In addition, the BMD of the tibia and femur were highest in the OVX-Gen-Si group compared with OVX-Gen and OVX-Si group (p < 0.05). After 10weeks treatment with genistein and silicon, the bone structure of ovariectomized rats was recovered, there was no difference of bone histomorphometric parameters between OVX-Gen-Si, OVX-E, and SHAM group (p > 0.05), and there was no difference in the concentration of serum ALP, Ca, P, OPG, and RANKL between OVX-Gen-Si, SHAM, and OVX-E groups (p > 0.05). RT-PCR showed that genistein and silicon treatment could effectively increase the OPG mRNA expression and decreased the RANKL mRNA expression compared to that of the OVX group (p < 0.05), the OPG/RANKL mRNA ratios were significantly decreased in the OVX group (p < 0.05), and it was nearly to normal in the OVX-Gen-Si group. Immunohistochemical staining results showed that genistein and silicon supplementation could effectively increase the protein expression of OPG and decrease the protein expression of RANKL in bone tissues; there were no significant differences in OPG and RANKL positive expression areas between OVX-Gen-Si, SHAM, and OVX-E group (p > 0.05). The results above indicate that genistein and silicon supplementation can effectively reduce RANKL, increase OPG levels, and OPG/RANKL ratios in the serum and bone tissue of ovariectomized rats; this is the main mechanism by which genistein and silicon play a bone protective role in ovariectomized rats.

Preventive and therapeutic effect of Corn Cervi Pantotrichum on bone tissue in ovariectomized rats through activation of BMP-2/Smads/Runx2 signal transduction pathway

Objective: Corn Cervi Pantotrichum, a traditional Chinese medicine, has been used to treat postmenopausal osteoporosis for a long time, but the mechanism is not clear. This study aimed to examine in detail the effects of Corn Cervi Pantotrichum on the bone of postmenopausal osteoporosisrat model. Materials and Methods: forty female rats were randomly divided into groups of: Sham operated (Sham), ovariectomized control, ovariectomized with Corn Cervi Pantotrichum and ovariectomized with ERT (Climen). The Corn Cervi Pantotrichum and ERT were administered through the route of oral gavage daily at the dose of 0.4 g.kg-1 and 0.2 mg.kg-1 respectively. Following 12 weeks of treatment, rats were anesthetized. The blood and the distal of left femur were for bone biomarker using Elisa. The right femur was measured for BMD (bone mineral density) and histopathological evaluation. The head of left femur were used for quantitative real-time PCR and Western blot. Results: Compared to the OVX group, supplementation of Corn Cervi Pantotrichum could not only increase the BMD of femur, but also increase the expression of bone formation maker. Photomicrograph of femur showed that Corn Cervi Pantotrichum can restore the normal architecture. Both Elisa, the quantitative real-time PCR and the Western blot results showed that Corn Cervi Pantotrichum may upregulates BMP-2/Smad1, 5/Runx2 expression in OVX rats. Conclusion: This confirmed that Corn Cervi Pantotrichum could be used for the prevention of postmenopausal osteoporosis.

Icariin improves osteoporosis, inhibits the expression of PPARγ, C/EBPα, FABP4 mRNA, N1ICD and jagged1 proteins, and increases Notch2 mRNA in ovariectomized rats.

Icariin (ICA) is a pharmacologically active flavonoid glycoside that shows promise in the treatment and prevention of osteoporosis (OP). However, the mechanisms underlying the anti-osteoporotic effects of ICA remain largely unclear. The present study used quantitative polymerase chain reaction, western blot and immunohistochemical analysis to examine the effects of ICA on several key targets in the Notch signaling pathway in bone tissue in ovariectomized rats. It was observed that ICA has a pronounced beneficial effect on OP rats and inhibits the expression of peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding protein α (C/EBPα) and fatty acid-binding protein 4 (FABP4) mRNA. In addition, it was identified that ICA downregulates the expression of notch1 intracellular domain (N1ICD) and Jagged1 proteins in bone tissue, and suppresses the effect of N1ICD on Notch2 mRNA expression. It is proposed that ICA inhibits the differentiation of mesenchymal stem cells into adipocytes by inhibiting the expression of PPARγ, C/EBPα and FABP4 mRNA via the Notch signaling pathway. In addition, it is proposed that ICA inhibits the expression of Notch2 mRNA by suppressing the effect of N1ICD. In conclusion, the results provide further mechanistic evidence for the clinical efficacy of ICA in the treatment of OP.

Opg/Rankl mRNA dynamic expression in the bone tissue of ovariectomized rats with osteoporosis

We established animal models of osteoporosis in ovariectomized rats to detect osteoprogerin (Opg)/receptor activator of nuclear factor-κB ligand (Rankl) mRNA expression levels in the tibias and serum estradiol concentrations at different time points. Sixty Sprague-Dawley female rats were randomly selected and divided into an ovariectomized (OVX) group and sham-operated (SHAM) group. In the SHAM group, only a small amount of abdominal fat and tissues was removed from the rats. Ten rats in each group were sacrificed at 0, 6, and 12 months after establishing the animal models (12 weeks). Opg mRNA expression and serum estradiol concentration in the OVX group were significantly lower than those in the SHAM group (P < 0.05). In contrast, Rankl mRNA expression in the OVX group was significantly higher than that in the SHAM group (P < 0.05). In the OVX group, Opg mRNA expression and serum estradiol concentrations decreased significantly from 0 to 12 months (P < 0.05), whereas Rankl mRNA expression increased significantly (P < 0.05). Opg mRNA expression and serum estradiol concentrations in the OVX group continually decreased, whereas Rankl mRNA expression continually increased. The Opg/Rankl ratio showed a decrease. The OPG/RANKL ratio may be a key factor affecting the osteoblast-mediated reaction.

Drynaria fortunei J. Sm. improves the bone mass of ovariectomized rats through osteocalcin-involved endochondral ossification

Aim of this studyOur previous study showed that Drynaria fortunei J. Sm. (Kunze), a traditional Chinese medical herb, can promote osteoblast differentiation and maturation. This study was further aimed to confirm the traditional effects of Kunze on the bone mass of ovariectomized rats. Materials and methodsFemale Wistar rats were given an ovariectomy and then administered the water extract of Kunze (WEK). Systemic and tissue toxicities of WEK were assessed. A biomechanical test, bone mineral contents, and bone histomorphometry were analyzed to determine the effects of the WEK on the bone mass. Levels of osteocalcin (OCN) in bone tissues were determined by immunohistochemistry and immunoblotting. The effects of naringin, one of the bioactive compounds of the WEK, on the bone mass were evaluated. ResultsA bilateral ovariectomy in rats caused a time-dependent decrease in levels of serum 17β-estradiol. Exposure of ovariectomized rats to the WEK at 0.5 and 1g/kg body weight/day for 1, 2, 3, and 6 months did not induce systemic or tissue toxicities. Biomechanical testing and a bone mineral content analysis showed that the ovariectomy decreased the bone torsion force and bone ash in time-dependent manners. In comparison, after exposure to the WEK, the ovariectomy-induced reductions in the bone torsion force and bone ash were significantly alleviated. In parallel, results of a bone histomorphometric assay further revealed that the ovariectomy caused significant diminution in the production of prehypertrophic chondrocytes and trabecular bone but enhanced hypertrophic chondrocyte numbers in the growth plate. However, exposure to the WEK lowered ovariectomy-induced changes in these cellular events. As to the mechanism, the WEK increased OCN biosynthesis in bone tissues of ovariectomized rats. Administration of naringin to ovariectomized rats caused significant amelioration of the bone strength, bone mineral contents, and trabecular bone amounts. ConclusionsThis study shows that the WEK can translationally promote the bone mass in ovariectomized rats through stimulating OCN-involved endochondral ossification.

The effect of zinc deficiency and zinc supplementation on element levels in the bone tissue of ovariectomized rats: Histopathologic changes

Objective: Study aimed to determine the effects of zinc supplementation/deficiency on the histological structure and elements levels in bone tissue in ovariectomized rats.Methods: The study included 40 Sprague-Dawley type adult female rats, divided as follows: Control, ovariectomized, ovariectomized + zinc supplemented, ovariectomized + zinc deficient groups. At the end of the study bone tissues (femur) were collected to determine the levels of calcium, phosphorus, magnesium, zinc, iron, aluminium, chrome, lithium, lead, nickel, and manganese. The bone tissue was examined for histopathology.Results: Ovariectomy leaded to significant decrease in magnesium. Zinc supplementation to ovariectomized rats restored the reduced calcium, phosphorus, zinc. However, zinc deficiency in ovariectomized rats further reduced calcium, phosphorus, zinc, and manganese levels. Zinc deficiency in ovariectomized significantly increased Al, Cr, Li, Pb, and Ni levels. Tissue integrity was impaired due to ovariectomy and zinc deficiency.Conclusion: Ovariectomy and zinc deficiency leads significant decreases elements of the bone.

EFFECTS OF SIMVASTATIN ON FEMORAL BIOMECHANICS IN OVARIECTOMIZED RATS

Objective: To investigate the effect of simvastatin on the biomechanical characteristics of the femur in ovariectomized rats. Material and methods: Fifty-four female Sprague-Dawley rats, aged three months old, were randomly divided into three groups: sham-operated group ( SHAM; n = 18), ovariectomized group (OVX; n = 18), and ovariectomized with simvastatin treatment group (OVX+SIM; n = 18). Eight weeks after being ovariectomized, simvastatin was administered orally at 5 mg/kg each day in the OVX + SIM group. The animals were sacrificed at either four or 12 weeks after administration and femurs were obtained. Biomechanical parameters were measured by the three-point bending test. Results: There were no significant differences in the maximal strain and flexibility strain between the OVX and OVX + SIM groups at either four or 12 weeks after administration (p &gt; 0.05). In contrast, significant differences in flexibility loading at four weeks and in maximal loading, flexibility loading, and the coefficient of bending ductility between the OVX and OVX + SIM groups at either four or 12 weeks (p &lt; 0.05 and p &lt; 0.01, respectively). Intergroup comparisons showed that maximal loading and flexibility loading have significant differences in the OVX + SIM group (p &lt; 0.01). Conclusion: Simvastatin shows potential in promoting bone remodeling, changing bone micro-architecture, and influencing the integration and distribution ratio of organic and inorganic constituents in bone tissue of ovariectomized rats. In addition, a longer time of administration with simvastatin could enhance the femoral strength.

Flaxseed combined with low-dose estrogen therapy preserves bone tissue in ovariectomized rats

Flaxseed is rich in lignans and alpha-linolenic acid, compounds that may promote healthy skeletons. Many postmenopausal women consume complementary health products such as flaxseed or its components in addition to pharmacological agents such as low-dose estrogen therapy for additional support for menopausal symptoms and related conditions. However, their combined effect on bone health is unknown. The aim of this study was to determine the effects of 10% dietary flaxseed, low-dose estrogen therapy, or their combination on bone mineral density, biomechanical strength, and skeletal fatty acid composition in an ovariectomized rat model of postmenopausal osteoporosis. Ovariectomized rats received (1) basal diet (negative control), (2) 10% flaxseed, (3) low-dose estrogen implant (13 microg, 90 day release), or (4) flaxseed + low-dose estrogen implant for 12 weeks. A sham-operated group was included as a positive control. Bone mineral density, biomechanical strength, and fatty acid composition were measured at multiple skeletal sites. Flaxseed + low-dose estrogen therapy resulted in the highest bone mineral density and peak load at the lumbar vertebrae, with no effect on bone mineral density or strength in the tibia and femur. Flaxseed and flaxseed + low-dose estrogen therapy resulted in significantly higher relative levels of alpha-linolenic acid and eicosapentaenoic acid and lower levels of linoleic acid, arachidonic acid, and n-6/n-3 ratio in the lumbar vertebrae and tibia compared with all other groups. Flaxseed + low-dose estrogen therapy provides the greatest protection against ovariectomy-induced bone loss at the lumbar vertebrae. Moreover, this study is the first to demonstrate that flaxseed, rich in alpha-linolenic acid, alters fatty acid composition in the ovariectomized rat skeleton.

Effects of soybean isoflavones on expression levels of osteoprotegerin and osteoprotegerin ligand mRNAs in bone tissues of ovariectomized rats

To investigate the effects of soybean isoflavones (SI) on expression levels of osteoprotegerin (OPG) and osteoprotegerin ligand (OPGL) mRNAs in bone tissues of ovariectomized rats, and to discuss the mechanism of soybean isoflavaones in preventing and treating postmenopausal osteoporosis (PMO). Thirty adult SD rats were randomly divided into 3 groups: sham-operation group, untreated group and SI-treated group. The rats in the last two groups were bilaterally ovariectomized. The bone density of L(3) to L(6) vertebrae was detected after 12-week intervention. Total RNA was extracted from femur head and the expression levels of OPG and OPGL mRNAs were examined by real-time quantitative polymerase chain reaction. SI could increase the bone density of lumbar vertebrae in ovariectomized rats, up-regulate the expression level of OPG mRNA and down-regulate the ratio of OPGL mRNA/OPG mRNA, but exert no significant effect on the expression of OPGL mRNA. The therapeutic effects of SI on PMO may be related to regulating the expression levels of OPG and OPGL mRNAs, and the ratio of OPGL mRNA/OPG mRNA.

The effects of zinc deficiency and supplementation on lipid peroxidation in bone tissue of ovariectomized rats.

This study aims at investigating how zinc deficiency and zinc application affect lipid peroxidation in bone tissue of ovariectomized rats. The study included 40 adult female rats of Sprague-Dawley species. Group 1 (n = 10): control group were fed with normal diet. Group 2 (n = 10): the group fed with normal diet after being ovariectomized. Group 3 (n = 10): the group fed with zinc-deficient diet for 6 weeks after ovariectomy. Group 4 (n = 10): the group which was given intraperitoneal zinc (3 mg/kg day zinc) in addition to normal diet for 6 weeks after ovariectomy. Malondialdehyde (MDA) and glutathione (GSH) levels were determined in erythrocyte, plasma and bone tissue. Group 3 had the highest plasma MDA levels compared to Groups 1, 2 and 4 (P < 0.05). These values were higher in Group 2 than in Groups 1 and 4 (P < 0.05). Bone and plasma MDA levels in Groups 1 and 4 were not different. Bone and erythrocyte GSH levels in Group 4 were higher than those in all other groups (P < 0.05). The lowest levels of bone and erythrocyte GSH levels were observed in Group 3 (P < 0.05). These values were higher in Group 2 when compared to those in Groups 1 and 3 (P < 0.05). This study demonstrate that zinc deficiency increased bone tissue damage in ovariectomized rats and that zinc supplementation prevented this damage.

Vertebral trabecular bone microscopic tissue elastic modulus and hardness do not change in ovariectomized rats.

Ovariectomized rats have been used extensively and have received substantial acceptance as animal models for postmenopausal osteoporosis. However, little is known about the microscopic tissue properties of rat vertebral bone, especially during osteoporosis caused by estrogen depletion. This study applied a new nanoindentation technique to quantify the microscopic mechanical properties of vertebral trabecular bone tissue in ovariectomized rats. Seventeen-week-old Sprague-Dawley rats underwent an ovariectomy. After death at 37 weeks, the fraction of the trabecular bone area of the lumbar vertebrae (L4) was measured with scanning electron microscopy and the elastic modulus and hardness were determined with the nanoindentation technique. The bone area fraction was reduced significantly after the ovariectomy. However, the elastic modulus and hardness did not change significantly at the microscopic level. The results indicate that estrogen-dependent osteoporosis in rats manifests in a loss of bone mass whereas the elastic and hardness properties of the surviving bone tissue remain relatively unchanged.

Distribution of menaquinone-4, a therapeutic agent for osteoporosis, in bone and other tissues of rats.

[14C]Menaquinone-4 was administered orally once daily at a dose of 4 mg/kg for ten days to female rats of different ages to determine its blood and tissue distribution with particular attention to its distribution in bone. Animals aged 10 and 30 months were either ovariectomized or sham-operated as a control, and young rats aged 7 weeks were used as untreated controls. Blood concentrations of radioactivity at 24h after each dose during repeated administration increased daily and approached a steady rate by the seventh dose. Higher concentrations of radioactivity in blood (plasma) were observed in older animals than in the younger ones, but there was little difference between ovariectomized rats (OVX rats) and sham-operated rats (Sham rats). In tissue samples collected at 1.5 h after administration, the liver, adipose tissue, spleen and adrenals showed higher concentrations of radioactivity than the other organs and the plasma. IN bone tissues, the bone marrow (BM) and cancellous tissue (CT) of the femur showed radioactivity concentrations which were higher than that in the plasma, and these increased during repeated administration. Finally, at 24 h after the last dose, the concentrations of radioactivity in bone tissues of older animals (BM, 5,807.2 ng eq/g; CT, 5,264.8 ng eq/g in OVX rats aged 10 months and BM, 11,479.3 ng eq/g; CT, 4,023.0 ng eq/g in OVX rats aged 30 months) were several times higher than those in younger animals (BM, 2,771.6 ng eq/g; CT, 890.2 ng eq/g in 7-week-old untreated rats). The values in OVX rats were also higher than those in Sham rats. Furthermore, micro autoradiography studies of femur sections from OVX rats indicated that [14C] Menaquinone-4 localized in cancellous tissue where bone is known to be actively remodelled. The concentrations of radioactivity in cancellous tissue and bone marrow of OVX rats aged 10 and 30 months were comparable to the pharmacologically effective concentrations of Menaquinone-4 (10(-6)-10(-5) M) in in vitro studies on bone formation. These findings suggest that orally administered Menaquinone-4 distributes specifically into the bone tissues of ovariectomized rats and this is consistent with its effect as a therapeutic agent for osteoporosis.