Effects of ovariectomy in beagle dogs

Demographic factors associated with joint supplement use in dogs from the Dog Aging Project

Osteoarthritis (OA) is one of the most prevalent age-related chronic conditions that afflict companion dogs, and multiple joint supplements are available to prevent or treat OA, though the efficacy of these treatments is controversial. While the demographic factors that are associated with OA diagnosis are well established, the factors that are associated with joint supplement use are not as well studied. Using data collected from the Dog Aging Project, we analyzed owner survey responses regarding joint supplement administration and OA diagnosis for 26,951 adult dogs. In this cross-sectional analysis, logistic regression models and odds-ratios (OR) were employed to determine demographic factors of dogs and their owners that were associated with joint supplement administration. Forty percent of adult dogs in our population were given some type of joint supplement. Perhaps not surprisingly, dogs of older age, larger size, and those that were ever overweight were more likely to receive a joint supplement. Younger owner age, urban living, owner education, and feeding commercial dry food were associated with a reduced likelihood of administration of joint supplements to dogs. Interestingly, mixed breed dogs were also less likely to be administered a joint supplement (OR: 0.73). Dogs with a clinical diagnosis of OA were more likely to receive a joint supplement than those without a reported OA diagnosis (OR: 3.82). Neutered dogs were more likely to have a diagnosis of OA, even after controlling for other demographic factors, yet their prevalence of joint supplement administration was the same as intact dogs. Overall, joint supplement use appears to be high in our large population of dogs in the United States. Prospective studies are needed to determine if joint supplements are more commonly administered as a preventative for OA or after an OA clinical diagnosis.

Dose-Dependent Clinical, Radiographic, and Histopathologic Changes of 17β-Estradiol Levels Within the Temporomandibular Joint: An Experimental Study in Ovariectomized Dogs

PURPOSE

The aim of this study was to test the hypothesis that the dose of estrogen replacement therapy may have an influence on the clinical, radiographic, and histopathologic changes within the temporomandibular joint (TMJ).

MATERIALS AND METHODS

A prospective experimental study was conducted in 12 mature ovariectomized dogs. Dogs were randomly allocated into 1 of 4 groups (OVX-E0, dogs that did not receive any estrogen replacement therapy; OVX-E0.5, dogs that received 0.15 mg/kg of estradiol; OVX-E1, dogs that received 0.3 mg/kg of estradiol; and OVX-E2, dogs that received 0.6 mg/kg of estradiol); dogs were evaluated clinically for 12 weeks; and contact radiographic and histopathologic examinations of the TMJ were performed just after euthanasia.

RESULTS

Radiographic examination of the TMJ in the OVX-E0 group showed narrowing of the joint space with marginal osteophyte formation along the mandibular condyle. The OVX-E0.5 group showed mild widening of the joint space with no remarkable changes within the mandibular fossa or condyle. The OVX-E1 group was free of radiographic changes within the TMJ. High doses of estrogen in the OVX-E2 group showed marked flattening of the mandibular condyle and fossa with sclerosis of the subchondral bone. Histopathologic sections in the OVX-E0 group showed thin compact bone with scanty, less organized lacunae. The OVX-E0.5 group showed compact bone of medium thickness with large osteons and disorganized lacunae. The OVX-E1 group showed thick compact bone with reduced intertubercular spaces and organized lacunae. The OVX-E2 group showed thin bone with reduced trabecular and increased intertrabecular thickness. The collagen content did not change significantly among the 4 groups, whereas its quality changed significantly (P < .05).

CONCLUSIONS

Estrogen dosage is potentially a key regulator of bone metabolism within the TMJ. Estrogen replacement therapy exhibited an inverted U-shaped beneficial effect. Estrogen depletion as well as high doses of estrogen resulted in clinical, radiographic, and histopathologic changes within the TMJ. Estrogen replacement therapy should be prescribed at the optimum dose when indicated as hormonal replacement therapy.

Effects of sequential treatment with intermittent parathyroid hormone and zoledronic acid on particle-induced implant loosening: Evidence from a rat model

Particle-induced implant loosening is a major challenge to long-term survival of joint prostheses. Administration of intermittent parathyroid hormone (PTH) has shown potential in the treatment of cases of early-stage periprosthetic osteolysis, while sequential administration of intermittent PTH (iPTH) and bisphosphonates (Bps) has achieved significant effects on treatment of postmenopausal osteoporosis. The objective of this study was to determine whether sequential treatment could preserve bone mass and implant fixation during a pathological course of peri-implant osteolysis in a rat model. Ninety male Sprague Dawley rats were randomly divided into nine groups, four of which were used for confirmation of establishment of the peri-implant osteolysis model at two time points, while the other five were used to determine the efficiency of the sequential treatment on peri-implant osteolysis. Implant fixation and peri-implant bone mass were evaluated using biomechanical testing, micro-CT analysis, and histology at 6 and 12 weeks postoperative. The biomechanical test demonstrated that the maximum loading force during a push-out test was significantly elevated in the sequential treatment group compared to the osteolysis group and iPTH withdrawal group at 12 weeks. Peri-implant bone morphology also indicated a robust increase in bone volume in the sequential treatment group. Sequential administration of iPTH and Bps was effective in preventing experimental peri-implant osteolysis, resulting in improved implant fixation and increased peri-implant bone volume. Clinical significance: The innovative application of sequential treatment in peri-implant osteolysis could be used clinically to improve the prognosis of patients with early-stage periprosthetic osteolysis. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1489-1497, 2019.

Rabbit as model for osteoporosis research

Osteoporosis is a major public health problem affecting more than 200 million people worldwide. The use of different animal models, for the study of its pathophysiology and treatments, is important being actually the ovariectomized rat the most widely used; although this model has several problems due its small size, lack of true closure of epiphyseal plate and bone differences with humans. This review is aimed at summarizing the most common methods published for osteoporosis induction in rabbits as model for human disease with their advantages and disadvantages. The paper shows the advantages of the use of this specie compared with the rat. All the techniques seemed to achieve the osteoporotic condition, but the one which obtained the most consistent bone mineral reduction in less time was the combination of surgery and corticoid treatment. The conclusion of the review was that rabbits are promising as a model of osteoporosis research because of their size, haversian remodelling and closure of epiphyseal plate, which solve some of the problems of the rat model. There are different techniques in the literature used to achieve the osteoporotic condition with diverse results, but there is a lack of consensus as to the best one.

Ovariectomy Impairs Socio-Cognitive Functions in Dogs

Simple Summary

The aim of this study was to test whether ovariectomy in dogs (Canis lupus familiaris) could impair a female’s ability in a socio-cognitive task. Forty pet dogs (18 intact females (IF) and 22 gonadectomized females (GF)) were tested in the object choice task paradigm using a human proximal pointing gesture. For the analysis, the frequency of correct, wrong and no-choices was collected; moreover, the latency of the correct choices was also considered. The IF group followed the pointing gestures more often than the GF group and with a lower latency whereas a significantly higher no-choice frequency was recorded for the GF group.

Abstract

Recent studies have underlined the effect of ovariectomy on the spatial cognition of female dogs, with ovariectomized dogs showing a clear preference for an egocentric rather than an allocentric navigation strategy whereas intact females did not show preferences. Intact females had better performances than gonadectomized females in solving a learning task in a maze. Ovariectomy also affects socio-cognitive abilities, reducing the dog’s level of attention on the owner. We tested dogs (Canis lupus familiaris) in the object choice task paradigm to assess whether an ovariectomy could impair females’ ability to follow human signals. Forty pet dogs (18 intact females (IF) and 22 gonadectomized females (GF)) were tested in the object choice task paradigm using the human proximal pointing gesture. For the analysis, the frequency of correct, wrong and no-choices was collected; moreover, the latency of the correct choices was also considered. The IF group followed the pointing gestures more often than the GF group and with a lower latency, whereas a significantly higher no-choice frequency was recorded for the GF group. These results show a detrimental effect of ovariectomy on dogs’ socio-cognitive skills related to the responsiveness to human pointing gestures.

Bisphosphonates and atypical subtrochanteric fractures of the femur

OBJECTIVES

Bisphosphonates are widely used as first-line treatment for primary and secondary prevention of fragility fractures. Whilst they have proved effective in this role, there is growing concern over their long-term use, with much evidence linking bisphosphonate-related suppression of bone remodelling to an increased risk of atypical subtrochanteric fractures of the femur (AFFs). The objective of this article is to review this evidence, while presenting the current available strategies for the management of AFFs.

METHODS

We present an evaluation of current literature relating to the pathogenesis and treatment of AFFs in the context of bisphosphonate use.

RESULTS

Six broad themes relating to the pathogenesis and management of bisphosphonate-related AFFs are presented. The key themes in fracture pathogenesis are: bone microdamage accumulation; altered bone mineralisation and altered collagen formation. The key themes in fracture management are: medical therapy and surgical therapy. In addition, primary prevention strategies for AFFs are discussed.

CONCLUSIONS

This article presents current knowledge about the relationship between bisphosphonates and the development of AFFs, and highlights key areas for future research. In particular, studies aimed at identifying at-risk subpopulations and organising surveillance for those on long-term therapy will be crucial in both increasing our understanding of the condition, and improving population outcomes.Cite this article: N. Kharwadkar, B. Mayne, J. E. Lawrence, V. Khanduja. Bisphosphonates and atypical subtrochanteric fractures of the femur. Bone Joint Res 2017;6:144-153. DOI: 10.1302/2046-3758.63.BJR-2016-0125.R1.

Raman spectroscopic investigation on the molecular structure of apatite and collagen in osteoporotic cortical bone

This study employed highly spectrally resolved Raman spectroscopy to examine the molecular composition of cortical bone tissue obtained from murine females in their healthy and ovariectomy- (OVX-) induced osteoporotic states. The aim of the study was to identify structural differences at the molecular scale both in apatite mineral and collagen fibrils between the two groups of samples. Raman spectroscopy was used to determine the chemical composition of cortical bone in regions including characteristic bands of both bone mineral and bone matrix. The results demonstrated that the mineral apatite of bone did not undergo significant amorphization in its diseased state, with the Raman microprobe also failing in recognizing a direct role of carbonate content in the embrittlement of OVX-diseased bone. On the other hand, complex off-stoichiometry variations could be detected in the columnar Ca-structure of the bony hydroxyapatite according to morphological variations of the Raman band belonging to the symmetric phosphate stretching (A₁) band at ~959cm^-1. A fundamental role was also recognized for collagen quality on the process of bone embrittlement. The so-called matrix maturity ratio, as systematically measured on Raman spectra in the Amide I region, increased with statistical significance in OVX-treated samples as compared to control samples. An 8% increase could be associated to a 115% increase in elastic stress intensification in the mineral phase of OVX-diseased tissue as compared to the control one, thus proving a degradation in the (elastic) energy-dissipative capacity of a diseased bone matrix.

Can we induce osteoporosis in animals comparable to the human situation?

Osteoporosis is a chronic systemic bone disease of growing relevance due to the on-going demographic change. Since the underlying regulatory mechanisms of this critical illness are still not fully understood and treatment options are not satisfactorily resolved, there is still a great need for osteoporosis research in general and animal models in particular. Ovariectomized rodents are standard animal models for postmenopausal osteoporosis and highly attractive due to the possibility to specifically modify their genetic background. However, some aspects can only be addressed in large animal models; such as metaphyseal fracture healing and advancement of orthopedic implants. Among other large animal models sheep in particular have been proven invaluable for osteoporosis research in this context. In conclusion, today we are able to influence the bone metabolism in animals causing a more or less pronounced systemic bone loss and structural deterioration comparable to the situation found in patients suffering from osteoporosis. However, there is no perfect model for osteoporosis, but a variety of models appropriate for answering specific questions. Though, the appropriateness of an animal model is not only defined in regard to the similarity to human physiology and the disease itself, but also in regard to acquisition, housing requirements, handling, costs, and particularly ethical concerns and animal welfare.

Osteoporotic risk and physeal closure in prepubertal ovariohysterectomized cats

We aimed to examine the early effects of prepubertal ovariohysterectomy (P-OHE) on bone loss and proximal physeal closure in cats. Fourteen kittens randomly underwent P-OHE or sham operations (S-OP) at three months (mo) of age and were allocated to group I and group II. Each mo between four and nine mo of age, dual-energy X-ray absorptiometry (DEXA) scans were performed to determine the total body bone mineral density (BMD) and bone mineral content (BMC). Proximal radial physeal closure and radial length were determined by radiography. Bone-specific alkaline phosphatase (BAP), carboxy-terminal collagen teleopeptide (CTX), 17-β estradiol, progesterone, calcium (Ca) and phosphorus (P) were measured in the serum samples. No significant differences were observed between the groups in terms of BMD, BMC, BAP, BAP/CTX, P, progesterone and body weight (BW) (between 4 and 9mo) and for Ca (between 5 and 9mo) and for CTX levels (between 4 and 8mo). The 17-β estradiol was significantly higher at 6, 8 and 9mo of age in the S-OP group due to puberty (P=0.02, P=0.03 and P=0.02 respectively). Although there was a significant difference (P=0.0002) between the P-OHE and S-OP groups in terms of the proximal radial physeal closure times (7.43±0.20mo and 6.14±0.14mo, respectively), no significant difference was observed for the mean radius length (10.59±0.10cm and 10.06±0.27cm, respectively) at the last evaluation time. In conclusion, prepubertal ovariohysterectomized cats do not have any osteoporotic risks until nine mo of age and exhibit a delayed physeal closure time without a change in radius length.

Duration-dependent effects of clinically relevant oral alendronate doses on cortical bone toughness in beagle dogs

Bisphosphonates (BPs) have been shown to significantly reduce bone toughness in vertebrae within one year when given at clinical doses to dogs. Although BPs also reduce toughness in the cortical bone when given at high doses, their effect on cortical bone material properties when given at clinical doses is less clear. In part, this may be due to the use of small sample sizes that were powered to demonstrate differences in bone mineral density rather than the bone's material properties. Our lab has conducted several studies in which dogs were treated with alendronate at a clinically relevant dose. The goal of this study was to examine these published and unpublished data collectively to determine whether there is a significant time-dependent effect of alendronate on toughness of the cortical bone. This analysis seemed particularly relevant given the recent occurrence of atypical femoral fractures in humans. Differences in the toughness of ribs taken from dogs derived from five separate experiments were measured. The dogs were orally administered saline (CON, 1ml/kg/day) or alendronate (ALN) at a clinical dose (0.2mg/kg/day). Treatment duration ranged from 3months to 3years. Groups were compared using ANOVA, and time trends analyzed with linear regression analysis. Linear regressions of the percent difference in toughness between CON and ALN at each time point revealed a significant reduction in toughness with longer exposure to ALN. The downward trend was primarily driven by a downward trend in post-yield toughness, whereas toughness in the pre-yield region was not changed relative to CON. These data suggest that a longer duration of treatment with clinical doses of ALN results in deterioration of cortical bone toughness in a time-dependent manner. As the duration of treatment is lengthened, the cortical bone exhibits increasingly brittle behavior. This may be important in assessing the role that long-term BP treatments play in the risk of atypical fractures of the femoral cortical bone in humans.

Calcium-phosphonate interactions: solution behavior and Ca2+ binding by 2-hydroxyethylimino-bis(methylenephosphonate) studied by multinuclear NMR spectroscopy

The tetra-acid 2-hydroxyethylimino-bis(methylenephosphonic acid) (HEIBPH, 1) and its ring condensation product, the triacid 2-hydroxy-2-oxo-4-phosphonemethyl-1,4,2-oxazaphosphorinane (2), were investigated for determination of protonation constants using (31)P, (1)H, and (13)C NMR spectroscopy in a wide pH range. As for other alpha-amino-phosphonic acids, the first protonation of 1 is straightforward and occurs at the nitrogen, while for 2 the first protonation occurs simultaneously at the exo phosphonate group, allowing estimation of the microscopic protonation constants. The complexation of Ca(2+) with 1 in a 1:1 molar ratio in aqueous solutions and in the presence of a 5-fold excess Na(+) is rationalized by the products LCaH(2), LCaH, LCaNaH, LCa, and LCa(2) (L = 1). Only the phosphonate groups are involved in Ca(2+) binding at pH > 3, while the phosphonate, hydroxyl, and amine functionalities coordinate to Ca(2+) at pH > 6-7, as soon as the proton at N is lost. Probable conformation states of ions of 1 and 2 are estimated by means of the dependence of vicinal coupling constants (3)J(HH) and (3)J(PC) from dihedral angles.

Review of nonprimate, large animal models for osteoporosis research

Large animal models are required for preclinical prevention and intervention studies related to osteoporosis research. The challenging aspect of this requirement is that no single animal model exactly mimics the progression of this human-specific chronic condition. There are pros and cons associated with the skeletal, hormonal, and metabolic conditions of each species that influence their relevance and applicability to human physiology. Of all larger mammalian species, nonhuman primates (NHPs) are preeminent in terms of replicating important aspects of human physiology. However, NHPs are very expensive, putting them out of reach of the vast majority of researchers. Practical, cost-effective alternatives to NHPs are sought after among ungulate (porcine, caprine, and ovine) and canine species that are the focus of this review. The overriding caveat to using large lower-order species is to take the time in advance to understand and appreciate the limitations and strengths of each animal model. Under these circumstances, experiments can be strategically designed to optimize the potential of an animal to develop the cardinal features of postmenopausal bone loss and/or yield information of relevance to treatment.

Estrogen deficiency and its effect on the jaw bones

Estrogen deficiency-induced postmenopausal osteoporosis has become a worldwide problem, inducing low bone mass and microarchitectural deterioration of the bone scaffolding in the vertebrae and long bones. With the prevalence of such osteoporosis on the increase, the influence of this estrogen deficiency on the jaw bones has drawn the attention of researchers and clinicians in the field of dentistry. The aim of this article is therefore to review the microstructural changes occurring after ovariectomy in the jaw bones of animal subjects. Induced estrogen deficiency clearly led to structural changes in the jaw bones and alveolar bone of animal subjects (rats and monkeys). Severe bone loss in the rat alveolar bone was principally caused by high bone resorptive activity. This activity accelerated greatly immediately after ovariectomy, and was then followed by more moderate resorptive activity, which continued over an extended period. Additionally, occlusal hypofunction further greatly accelerated the fragility of the alveolar bone structure in ovariectomized rats. Microstructural damage also seen in the alveolar bone of ovariectomized monkeys was found to be directly connected to their systemic osteoporosis. Recent investigations of the relationship in humans between systemic osteoporosis and jaw bone loss have also suggested that a connection may exist between these two. However, more research is required to confirm this connection in humans as well.

The use of bisphosphonates in cancer patients

Skeletal-related events resulting from bone metastases or osteoporosis can significantly contribute to morbidity and mortality in cancer patients. Expert opinion on the effectiveness of bisphosphonates in this setting is evolving. Here we review current evidence on the risks and benefits of bisphosphonate therapy for a wide variety of cancers, as well as clinical management of its adverse effects. A MEDLINE search of English-language literature (1966 through May 2006) was conducted using the terms bisphosphonate, cancer, multiple myeloma, malignancy, and randomized controlled clinical studies. Studies were selected based on clinical pertinence, with an emphasis on phase III clinical trials. We reviewed bibliographies for other relevant articles. Accumulating evidence reveals that bisphosphonate therapy has a significant effect in preventing skeletal complications in multiple myeloma, breast cancers, and prostate cancer, and in reducing skeletal complications in other metastatic bone malignancies. Emerging data indicate that bisphosphonates are useful for preventing bone loss resulting from cancer or its therapy. The efficacy of bisphosphonates for early-stage breast cancers remains controversial. Significant risks of bisphosphonate therapy include nephrotoxicity, electrolyte abnormalities, and osteonecrosis of the jaw. Bisphosphonate therapy has a clear role in the management of skeletal metastases associated with a variety of cancers. However, significant side effects require ongoing monitoring and treatment.

Short-term effects of prepubertal ovariohysterectomy on skeletal, physical and behavioural development of dogs up to 24 weeks of age

This study investigated the effects of ovariohysterectomy performed at 10 weeks of age on body weight, behaviour, bone length, serum calcium and phosphorus concentrations and gonadal hormone (progesterone and oestradiol) levels until 24 weeks of age in 31 clinically healthy mixed-breed female puppies. The littermates were randomly assigned to three groups. Group I (n=11) was completely ovariohysterectomised, Group II (n=10) was incompletely ovariohysterectomised with one ovary left intact, and Group III (n=10) was sham operated. No significant differences were found between the groups for any of the parameters evaluated. It was determined that, except for two measurements of two animals in Group II at 20 and 24 weeks of age, all animals had undetectable concentrations of oestradiol 17-beta. These findings suggest that an ovariohysterectomy performed on a mixed-breed dog at 10 weeks of age does not affect her skeletal, behavioural or physical development in the period studied, i.e. until 24 weeks of age.

Relationship between porotic changes in alveolar bone and spinal osteoporosis

Epidemiological studies have shown that post-menopausal women who do not use an estrogen supplement have fewer teeth than those who do. We hypothesized that changes in the dentition of post-menopausal women might be due to alveolar bone alterations by estrogen deficiency. To clarify this, we analyzed the microstructural alveolar bone changes in ovariectomized monkeys and compared these with their lumbar bone mineral density. The % of baseline bone mineral density showed a significant decrease in the ovariectomized group as compared with the controls. The second-molar interradicular septa in ovariectomized monkeys showed a significantly decreased nodes number, cortices number, and an increased structural model index value. More pores were seen in the ovariectomized group at the top of the septa. This study demonstrated that, in such monkeys, estrogen deficiency led to fragility of the trabecular structure of the molar alveolar bone, and such fragility was inversely correlated with lumbar bone mineral density.

The effect of prepubertal ovariohysterectomy on spine 1 mineral density and mineral content in puppies: A preliminary study

This pilot study investigated early effects of prepubertal ovariohysterectomy on bone mineral density (BMD) and bone mineral content (BMC) of lumbar vertebraes (L2-L5 and L Total) and on serum biochemistry. Both prepubertal ovariohysterectomy (Group Po: n=3) and sham surgery (Group Lp: n=3) were performed at 10 weeks of age. Blood samplings, BMD and BMC measurements of L2, L3, L4, L5 and L Total were performed at 12, 16, 20 and 24 weeks of age. No significant difference (P>0.05) in BMD and BMC was observed between the groups during the experimental period. The difference in serum calcium and phosphorus concentrations was found to be statistically unsignificant (P>0.05). These results fail to demonstrate a difference in BMD and BMC of lumbar vertebraes (L2-L5) as well as serum calcium and phosphorus levels after prepubertal ovariohysterectomy until six months of age in mixed breed puppies, but they should be considered only descriptive because of the very low sample number and of the low power of the statistical analyses.

The long-term effects of ovariectomy on bone metabolism in sheep

Osteoporosis and associated fractures are major public health concerns, and as such require appropriate large animal models to further our understanding of this disease. Although sheep appear to be an ideal model with which to study bone loss caused by estrogen depletion, limited data are available concerning the long-term effect of ovariectomy on bone in sheep. The goal of the present study was to observe the ovariectomy-induced changes in bone mass, structure, and metabolism in sheep over a period of 18 months. Six ewes were ovariectomized (OVX) and compared to an age-matched control group by analyzing bone mineral density, trabecular structure, biochemical markers of bone formation and resorption, and plasma estrogen levels. Bone loss (13%, P < 0.01) occurred during the first 4 months after surgery, then stabilized and returned to pre-OVX levels for the remainder of the study. Trabecular architecture was also altered and tended toward osteopenia with recovery to baseline values. Markers of bone formation and resorption were elevated up to 6 months postovariectomy, after which time levels returned to baseline values. Although estradiol measurements demonstrated a clear decline following surgical ovariectomy, levels returned to normal after 6 months. Therefore, the detrimental effect of ovariectomy on sheep bone metabolism seems to be reversible, with normal bone parameters being reestablished within 6 months after surgery. These data seem to indicate that the sheep is not an appropriate model for human postmenopausal osteoporosis.

Immunocytochemical Study of Amelogenin Deposition during the Early Odontogenesis of Molars in Alendronate-treated Newborn Rats

Newborn rats were treated with sodium alendronate to study how enamel is formed and the effect of alendronate during early odontogenesis. Ultrastructural analysis combined with high-resolution immunocytochemistry for amelogenin was carried out. Twelve rats were subjected to daily SC injections of sodium alendronate (2.5 mg/kg/day) for 3 days on their dorsal region, whereas three rats were daily injected with saline solution as a control. Molar tooth germs from 3-day-old rats were fixed under microwave irradiation in 0.1% glutaraldehyde + 4% formaldehyde buffered at pH 7.2 with 0.1 M sodium cacodylate. The specimens were left undecalcified, postfixed with osmium tetroxide, dehydrated, and embedded in LR White resin. Ultrathin sections were incubated with a chicken anti-24-kDa rat amelogenin antibody, a secondary antibody, and finally with a protein A-gold complex. Large patches of amelogenin were present over the unmineralized mantle dentin and at early secretory ameloblasts. At more advanced stages, they were also detected at the enamel matrix, as well as in the mineralized dentin, at the periodontoblastic space of the dentinal tubules, and at the predentin. It is likely that the main effect of alendronate at early stages of odontogenesis is the increase of synthesis/secretion of amelogenin, promoting its deposition within the forming dentin and enamel.

Genetic background influences cortical bone response to ovariectomy

Peak bone mass is genetically determined, but little is known about the heritability of bone loss. Inbred mice were ovariectomized at 16 weeks of age and killed at three time-points after surgery. We found that the variation in estrogen deficit-related cortical bone loss is genetically determined.

INTRODUCTION

Variability in adult bone morphology and composition among three inbred mouse strains-A/J, C57BL/6J (B6), and C3H/HeJ (C3H)-suggests that they gain bone in different ways during growth. In this study, we tested the hypothesis that these strains would also lose bone differently after estrogen deprivation.

MATERIALS AND METHODS

Female A/J, B6, and C3H mice (N = 70/strain) were either ovariectomized (OVX) or sham-operated at 16 weeks of age and killed at 4, 8, and 16 weeks after surgery. Cortical bone histomorphometry was performed on right femoral mid-diaphyseal cross-sections. Mechanical properties were determined by loading left femoral mid-diaphyses to failure in four-point bending.

RESULTS

Both OVX-A/J and OVX-B6 mice showed a 7-8% decrease in cortical area and width because of an 8-10% marrow expansion at 16 weeks after OVX. This bone loss did not affect mechanical properties in OVX-A/J femurs, but maximum load and stiffness in OVX-B6 decreased slightly (9%) at 4 and 8 weeks, and markedly (14-19%) at 16 weeks after OVX. In contrast, OVX-C3H showed a significant decrease in cortical area and width (6-7%) at 4 weeks after OVX and a slight decrease in the subperiosteal area (4%) at 8 weeks after OVX, although marrow area remained unchanged. Surprisingly, intracortical resorption spaces, which were present in sham-C3H mice, were greatly increased (+195%) in OVX-C3H mice at 8 weeks after OVX. Bone strength and stiffness in OVX-C3H mice decreased markedly (12-14%) at 4 weeks but slightly (8-10%) at 8 weeks after OVX. All indices except intracortical pore area in OVX-C3H mice returned to sham levels at 16 weeks after OVX.

CONCLUSIONS

The magnitude, timing, and location of cortical bone loss after OVX varied significantly among A/J, B6, and C3H mice. The subsequent changes in mechanical properties after OVX depended on the variable bone patterns as well as the size and shape of the adult bone. Our results suggest that patterns of estrogen deficit-associated cortical bone loss are genetically determined.

Preparation and characterization of new hybrid organic/inorganic systems derived from calcium (α-aminoalkyl)-phosphonates and -phosphonocarboxylates

We have studied the phenomenon of calcium complexation by lab synthesized amphiphilic (alpha-aminoalkyl)-phosphonocarboxylic or -phosphonic acids. The electrical conductivity of aqueous solutions of sodium salts of all these acids was measured versus the volume of a calcium salt solution added. It appeared that calcium complexes are formed in a Ca/P atomic ratio close to 1. Calcium phosphonocarboxylates and calcium phosphonates were also precipitated by mixing aqueous solutions of disodium salts of phosphorus amphiphiles and calcium nitrate solutions. Before chemical analysis, these complexes were calcined to remove the organic part. In the mineralized products, calcium and phosphate were assayed: the Ca/P atomic ratio was equal to 1. X-ray diffraction and IR spectroscopy showed that they are made entirely of beta pyrophosphate (Ca2P2O7), a result in agreement with previous chemical analysis. The chemical formula of the starting calcium complexes could be written as CaL2H2O (L=ligand). The SEM micrographs of these complexes show plate-like structures. XRD patterns are characteristic of layered structures. These facts suggest that calcium complexes are composed of alternating bimolecular layers of calcium alkylphosphonocarboxylates or calcium alkylphosphonates, the chains being tilted and partially interdigitated.

Animal models for fracture treatment in osteoporosis

Demographic changes in the age structure of occidental populations are giving rise to osteoporosis and associated fractures, which are becoming a major public health burden. Various animal models have been established and used to investigate the pathogenesis of osteoporosis and to facilitate the preclinical testing of new treatment options such as antiresorptive drugs. Although osteoporosis can be induced in animals, spontaneous fractures without adequate trauma were only found in nonhuman primates. An animal model designed to investigate new ways to treat fractures of osteoporotic bone has to fulfill requirements that are very different from those of pharmacological testing. The aspects of major interest in orthopedic applications are bone fragility, efficacy of implant fixation and bone healing. Existing animal models for osteoporosis were critically reviewed focusing on these aspects. The advantages and disadvantages of the models with regard to their application in the testing of new fracture-fixation devices or biological approaches to stimulate bone healing are discussed. Ovariectomy alone does not cause the bone loss seen in osteoporotic human patients. New models to simulate fracture of osteoporotic bone need to be explored and used to address the specific aims of an experiment.

Alendronate Therapy May Be Effective in the Prevention of Bone Loss Around Titanium Implants Inserted in Estrogen-Deficient Rats

BACKGROUND

This study evaluated whether alendronate (ALD) influences bone healing around titanium implants inserted in ovariectomized rats and whether it provides a residual effect after its withdrawal.

METHODS

Bilateral ovariectomies were performed in 87 Wistar rats and one screw-shaped titanium implant was placed in the tibiae. The animals were divided into the following groups: group SHAM (N = 15): sham surgeries; group OVX (N = 15): ovariectomy; group AT (N = 15): OVX plus alendronate administration for 80 days; group AW (N = 14): OVX plus alendronate administration for 40 days; group ET (N = 14): OVX plus 17beta estradiol administration for 80 days; or group EW (N = 14): OVX plus 17beta estradiol administration for 40 days. Bone-to-implant contact (BIC), bone area (BA) within the limits of implant threads, and bone density in a 500 microm-wide zone lateral to the implant (BD) were obtained and measured for the cortical (zone A) and cancellous (zone B) regions.

RESULTS

In zone A, data analysis showed no significant differences among the groups regarding BIC and BD (P >0.05), and a slight beneficial effect of estradiol on BA when compared with the OVX, EW, and AW groups (P <0.05). In zone B, OVX negatively impacted bone healing around the implants, resulting in reduced BA and BD (P<0.05). ALD (continuous/interrupted) and estradiol (only continuous) positively affected BIC, BA, and BD, resulting in values at the same level as the control group (SHAM).

CONCLUSIONS

ALD may prevent the negative influence of estrogen deficiency on bone healing around titanium implants inserted in OVX rats. This positive effect, in contrast to estradiol, is sustained following its withdrawal.

The ovariectomized sheep as a model for human bone loss

The aim of this study was to determine the effects of ovariectomy on the trabeculae of ovine iliac bone, with a view to the further development of a model for human osteoporosis. Seven ovariectomized (OVX) and five control Dorset ewes were observed for one year. Iliac crest bone samples were obtained at the time of ovariectomy ("time 0") and again when the animals were killed 12 months later. At "time 0" and at 3-month intervals thereafter samples of blood and urine were collected for the assay of serum 17beta-oestradiol and osteocalcin (OC) and urinary deoxypyridinium (D-PYR). One year after ovariectomy, trabecular bone volume and thickness were reduced (P<0.05) and trabecular separation was increased (P<0.05) as compared with the controls. In OVX sheep, serum 17beta-oestradiol concentrations were significantly lower at the end of the experiment than at "time 0", while serum OC and urinary D-PYR concentrations were significantly higher (P<0.001). The results suggest that the OVX sheep is a valid model for changes in trabecular bone architecture associated with oestrogen deficiency, especially in women experiencing early menopause.

Alendronate May Protect Against Increased Periodontitis-Related Bone Loss in Estrogen-Deficient Rats

BACKGROUND

The aim of this study was to evaluate the impact of alendronate (ALD) and estrogen (EST) therapies and their withdrawal on bone loss in experimental periodontitis in ovariectomized rats.

METHODS

Eighty-seven Wistar rats were divided into six groups: group 1 (N = 15): sham surgery; group 2 (N = 15): ovariectomy (OVX); group 3 (N = 15): OVX plus alendronate administration for 80 days (AT); group 4 (N = 14): OVX plus alendronate administration for 40 days (AW); group 5 (N = 14): OVX plus 17beta estradiol administration for 80 days (ET); and group 6 (N = 14): OVX plus 17beta estradiol administration for 40 days (EW). Twenty-one days after ovariectomy or sham surgery, one mandibular molar was randomly assigned to receive a ligature, while the contralateral tooth was left unligated. Sixty days later, the animals were sacrificed and the specimens processed.

RESULTS

OVX presented a direct impact on alveolar bone, regardless of plaque accumulation and significantly increased bone loss resulting from periodontitis (P < 0.05). The effect of OVX on unligated sites was significantly reduced by AT, AW, and ET (P < 0.05), but not by EW (P > 0.05). In addition, alendronate administration (AT/AW) significantly reduced the impact of OVX on periodontitis-related bone loss (P < 0.05), while estradiol did not (P > 0.05).

CONCLUSION

Within the limits of this study, alendronate administration, but not estrogen replacement, may protect against the impact of estrogen deficiency on alveolar bone presenting a significant residual effect after its withdrawal.

Comparative assessment of bone mineral measurements obtained by use of dual-energy x-ray absorptiometry, peripheral quantitative computed tomography, and chemical-physical analyses in femurs of juvenile and adult dogs

OBJECTIVE

To compare bone mineral measurements obtained by use of dual-energy x-ray absorptiometry (DEXA), peripheral quantitative computed tomography (pQCT), and chemical-physical analyses and determine effects of age and femur size on values obtained for the various techniques.

SAMPLE POPULATION

Femurs obtained from 15 juvenile and 15 adult large-breed dogs.

PROCEDURE

n each femur, 7 regions of interest were examined by use of DEXA to measure the bone mineral content (BMC) and bone mineral density (BMD), and 5 were examined by use of pQCT to measure BMD. Among these, 1 region was examined by both noninvasive methods and an invasive method. Volume of the femur was determined by water displacement. Volumetric bone density (VBD) was calculated. Calcium (Ca), phosphorus (P), total Ca, and total P contents were determined.

RESULTS

DEXA- and pQCT-derived results revealed that all values increased with age in juvenile dogs. In adults, VBD and pQCT-derived BMD decreased significantly and DEXA-derived BMD increased with increasing femur length. The pQCT-derived BMD correlated well with VBD and Ca content, whereas DEXA-derived BMC was strongly correlated with Ca content. In juveniles, values correlated regardless of the technique used, whereas in adult dogs, DEXA-derived BMD did not correlate with pQCT-derived BMD, Ca concentration, or VBD unless data were adjusted on the basis of femur length.

CONCLUSIONS AND CLINICAL RELEVANCE

DEXA-derived BMD adjusted for femur length yields approximately the same percentage variability in VBD as for pQCT-derived BMD. However, pQCT-derived BMD is still more sensitive for determining variability BMD in Ca concentration, compared with DEXA-derived BMD adjusted for femur length.

The Emerging Role of Bisphosphonates in Prostate Cancer

Bisphosphonates are a class of therapeutic agents originally designed to treat loss of bone density. It has been shown that the primary mechanism of action is inhibition of osteoclastic activity. Accumulating data show that these drugs are useful in diseases with propensities toward osseous metastases. In particular, they are effective in diseases in which there is clear upregulation of osteoclastic or osteolytic activity such as breast cancer and multiple myeloma. Despite the fact that osseous metastases in prostate cancer manifest as osteosclerosis rather than osteolysis, studies now show that bisphosphonates are useful in the management of this disease. In particular, they have demonstrated an impact on osteoporosis associated with hormonal therapy, bone pain from metastases, and skeleton-related events from prostatic adenocarcinoma. This review briefly summarizes the available clinical data on the utilization of bisphosphonates in the disease of prostate cancer.

Effect of parity on bone mineral density in female rhesus macaques from Cayo Santiago

This cross-sectional study investigates the relationship between parity, bone mineral density, and spontaneous osteopenia/osteoporosis in a large skeletal population of female rhesus macaques (Macaca mulatta) from the free-ranging colony of Cayo Santiago, Puerto Rico. The sample consists of 119 mature female monkeys aged 4.0-22.2 years at time of death. The data consist of measurements of bone mineral content (BMC) and bone mineral density (BMD), obtained from dual-energy X-ray absorptiometry (DEXA) of the last lumbar vertebra. After controlling for age, there is a significant increase in BMD of the spine with increasing parity (P = 0.0006), up to a parity of 7 offspring. Thus, high parity initially has a positive effect on BMD in female rhesus monkeys, but this positive effect disappears with parities that are greater than 7 offspring. After controlling for parity, however, age has a negative (P = 0.015) effect on BMD, beginning several years after the attainment of peak BMD (age 9.5 years). Thus, it appears that parity initially mitigates the effects of aging, but the positive effect of parity on BMD is eventually overwhelmed by the aging process. Mean BMC and BMD values are higher in parous females compared to nulliparous females in the same age range. Similarly, females with low parity have significantly lower mean BMD values than do age-matched high-parity controls, and the frequency of osteopenia and osteoporosis is greater in low-parity females. Forty-three percent (43%) of the osteopenic/osteoporotic females in the sample are members of the low-parity group, even though it composes only 13% (16/119) of the entire sample. This study demonstrates that the free-ranging female rhesus monkeys from Cayo Santiago are a good nonhuman primate model for the study of bone mineral density, parity, osteopenia, and osteoporosis.

Clodronate treatment of established bone loss in cardiac recipients: a randomized study

BACKGROUND

Bone loss has been reported as a complication after heart transplantation (HTx), and the increase in bone fractures is an effective problem. Treatment of osteoporosis has obtained mixed results. In this study we evaluate the effect of treatment with an oral bisphosphonate.

METHODS

Sixty-four patients with low mineral density 6 months after HTx were randomized as follows: Group A received oral clodronate (1600 mg/day in two divided doses), and Group B received placebo. Every patient was also treated with 2000 mg/day of oral calcium carbonate. Bone mineral density (BMD) was measured by dual energy x-ray absorptiometry at the lumbar spine, 1/3 and 1/10 of the distal nondominant forearm before and after 12 months of treatment. Laboratory tests were performed at 3, 6, and 12 months of treatment.

RESULTS

All patients demonstrated manifest bone loss 6 months after HTx compared with normal non-HTx controls (P=0.0001). After 1 year of clodronate therapy, BMD at the lumbar spine increased from 0.77+/-1.4 g/cm(2) to 0.86 g/cm(2) (P=0.02). Laboratory tests did not show any significant variation, except for the bone isoenzyme of alkaline phosphatase, which showed a significant decrease after 1 year of treatment. The incidence of new fractures was 9.3% in the placebo group and 0% in the clodronate group. Therapy was well tolerated without impact on graft function.

CONCLUSIONS

One year of clodronate therapy induced a significant increase in BMD at the lumbar spine in our HTx patients. Treatment was well tolerated without onset of new bone fractures.

Growth factor delivery for bone tissue engineering

Bone is a dynamic tissue that undergoes significant turnover during the life cycle of an individual. Despite having a significant regenerative capability, trauma and other pathological scenarios commonly require therapeutic intervention to facilitate the healing process. Bone tissue engineering, where cellular and biological processes at a site are deliberately manipulated for a therapeutic outcome, offers a viable option for the treatment of skeletal diseases. In this review paper, we aim to provide a brief synopsis of cellular and molecular basis of bone formation that are pertinent to current efforts of bone healing. Different approaches for engineering bone tissue were presented with special emphasis on the use of soluble (diffusible) therapeutic agents to accelerate bone healing. The latter agents have been used for both local bone repair (i.e. introduction of agents directly to a site of repair) as well as systemic bone regeneration (i.e. delivery for regeneration throughout the skeletal system). Critical drug delivery and targeting issues pertinent for each mode of bone regeneration are provided. In addition, future challenges and opportunities in bone tissue engineering are proposed from the authors' perspective.

Novel drug delivery system to bone using acidic oligopeptide: pharmacokinetic characteristics and pharmacological potential

We synthesized fifteen oligopeptides consisting of Asp or Glu conjugated with a fluorescent probe, 9- fluorenylmethylchloroformate (Fmoc). In the in vitro binding assay to putative hydroxyapatite (HA), the affinities of these conjugates depended only on the number of amino acid residues, not on their optical characters (L or D) or their species (Asp or Glu). In an in vivo experiment involving a single i.v. injection of Fmoc-D-Asp oligopeptides into mice, peptides consisting of over six Asp residues were selectively distributed to the bone. Then, we synthesized estradiol-17 beta-succinate-(L-Asp)6 [E2-(L-Asp)6] and studied its pharmacokinetic characteristics and its antiosteoporotic effects on ovariectomized (OVX) mice. Although the distribution volume of E2-(L-Asp)6 was significantly smaller than that of E2, E2-(L-Asp)6 was selectively distributed in the bone after i.v. injection and gradually decreased during 7 days. E2-(L-Asp)6 effectively prevented OVX-induced bone loss, without altering the uterine weight, in the dosage range of 0.11 to 1.1 mumol/kg once a week, while E2 increased both the bone mineral density and uterine weight at 0.37 mumol/kg every third day. The results suggest that acidic oligopeptide may be useful for drug delivery to bone and E2-(L-Asp)6 is a good candidate as an anti-osteoporosis drug without the adverse side effects of E2.

A histopathological investigation on the effects of the bisphosphonate alendronate on resorptive phase following mucoperiosteal flap surgery in the mandible of rats

BACKGROUND

The present study was designed to examine histopathologically whether local delivery of aminobisphosphonate (alendronate) could be effective in preventing the alveolar bone resorption associated with mucoperiosteal flaps.

METHODS

Following mucoperiosteal flap elevation in the molar region of the rat mandible, a surgical pellet soaked with aminobisphosphonate was locally applied on the exposed bone surface and covered by flap. The determined parameters with a semi-quantitative subjective method for the histopathological evaluation were as follows: existing inflammatory cell infiltration of the related periodontal tissue; fibrotic component content and bundles of collagen fibers; the number and morphology of osteoclasts of the alveolar bone and interdental septum; existing resorption lacunae (osteoclast surfaces); and existing osteoblastic activity (forming surfaces).

RESULTS

The results showed that while there were no detectable statistically significant differences between the saline and alendronate-treated groups on the existing inflammatory cell infiltration (ICI), number of osteoclasts, and osteoblastic activity, the results for the fibrotic and collagen component, osteoclast morphologies, and existing resorption lacunae were statistically significant.

CONCLUSIONS

These results suggest that local application of the aminobisphosphonate alendronate can be used as an adjunct in therapy for reducing bone resorption following surgery. It can also be suggested for consideration that, even for the surgical approaches in dentistry where bone graft materials and/or dental implants are needed, using bisphosphonate may achieve a new dimension in periodontal therapy in the near future.

Effects of orchidectomy on bone metabolism in beagle dogs

The effects of orchidectomy on bone metabolism in male beagle dogs were examined using twelve 2-year-old dogs that were orchidectomized. The dogs' bilateral iliac bones, double-labeled with tetracycline and calcein for the histomorphometry, were obtained from three dogs prior to orchidectomy and at 3, 6, 9, and 12 months afterwards. The serum biochemical constituents related to bone metabolism were examined before and every month after orchidectomy. Between 1 and 6 months after orchidectomy, the value of serum testosterone decreased (1 month), while the levels of parathyroid hormone, calcitonin, total calcium, osteocalcin, and alkaline phosphatase activity increased significantly, indicating a high bone turnover. The mean trabecular thickness and the fraction of labeled osteoid surface decreased significantly 3 months after orchidectomy, but other histomorphometric parameters were unchanged. In the period 7-12 months after orchidectomy, the parathyroid hormone level increased ever and above that of the first 6-month period, while the levels of calcitonin, osteocalcin, alkaline phosphatase activity, and phosphorus decreased. The bone volume, mean trabecular thickness, and the fraction of labeled trabecular surface decreased significantly compared with the pre-orchidectomy values. These findings indicate an imbalance in bone metabolism (i.e. bone resorption > bone formation). These results indicate that a loss of bone volume accompanied the fall in sex hormone levels following orchidectomy and suggest that the orchidectomized dog is available as an animal model for studying osteoporosis caused by hypogonadism and the decline of sex functions in men.

Do more highly organized collagen fibrils increase bone mechanical strength in loss of mineral density after one-year running training?

The aim of this study was to evaluate the effects of long-term running training on the structural properties of bone. Ten beagle dogs ran according to a strenuous progressive program (up to 40 km/day) for 1 year. At the end of the training program, there was a significant reduction in bone mineral density (up to 9.7%) in the vertebrae of the runner dogs as compared with 10 sedentary control dogs. Polarized light microscopy of the vertebral trabecular bone, however, displayed proportionally higher retardation values of the collagen network of the runner dogs than of the sedentary dogs, suggesting a reorganization in a more parallel manner in the collagen fibrils. The concentration and cross-linking of collagen in the bones remained similar in both groups. No differences were observed in the force to failure of bones of the two groups nor in the histomorphometric analysis of the bones. We suggest that the collagen network in the bones accounted for the maintenance of the strength properties in the bones of the runner dogs despite the loss of mineral density.

Synthesis, Characterization, and Crystal Structure of Dicalcium Glutarylbis(phosphonate) Dihydrate: A Covalently Pillared Layer Structure with the Potential for Epitaxial Growth on Hydroxyapatite

A new bis(acylphosphonate), glutarylbis(phosphonate) (GlBP), was synthesized. Sodium and calcium salts of the GlBP, disodium dihydrogen glutarylbis(phosphonate), NaHO(3)PC(O)(CH(2))(3)C(O)PO(3)HNa, and dicalcium glutarylbis(phosphonate) dihydrate, Ca(2)[O(3)PC(O)(CH(2))(3)C(O)PO(3)].2H(2)O, were prepared and characterized by chemical analyses, thermogravimetry and Fourier transform infrared spectroscopy (FTIR). The crystal structure of the Ca salt was determined by single-crystal X-ray diffraction. The crystals are orthorhombic with a = 10.970(1) Å, b = 23.694(2) Å, c = 5.580(1) Å, space group Pnma, and Z = 4. This study provides the first example of a structure of a calcium complex involving a nongeminal bis(phosphonate). The structure can be described in terms of a covalently pillared layer-type arrangement of neutral Ca-GlBP-Ca units along the b-axis. Each oxygen atom of the phosphonate group is bonded to a different Ca ion, and each Ca in turn is linked to three phosphonate groups. The Ca octahedra and the phosphonate tetrahedra form a two-dimensional polar sheet perpendicular to the b-axis. The chelate bonds involving the keto groups appear to be important links in the stabilization of the structure and, in turn, to the biological activity of bis(acylphosphonates). A near-perfect lattice match, found between the Ca phosphonate layer and the major crystal faces of hydroxyapatite, indicates that epitaxial growth or incorporation of GlBP can occur on the apatitic surface which may be the mode of action in the inhibition of calcification.

Changes in canine cortical and cancellous bone mechanical properties following immobilization and remobilization with exercise

The purpose of this study was to assess cortical and cancellous bone responses to unilateral limb immobilization and, subsequently, to remobilization with exercise, in a young adult canine model. Right forelimbs of 14 1-2-year old mongrel dogs were immobilized in a non-weight-bearing position by a bandage for 16 weeks. Six control dogs were untreated. At 16 weeks, seven immobilized and three control dogs were euthanized. The remaining seven immobilized dogs began a recovery protocol consisting of 16 weeks of kennel confinement (without the right forelimb bandaged) followed by 16 weeks of treadmill exercise conducted three times per week. These seven dogs and three control dogs were euthanized at 48 weeks. Bone mineral density of the proximal radii was determined with dual-energy X-ray absorptiometry and humeral middiaphyseal cross-sectional areas were determined with computed tomography. Humeri were tested in cranio-caudal three-point bending to failure. Cancellous bone cores from the lateral humeral condyles had wet apparent density determined and were tested to failure in compression. Mechanical properties, bone density, and cross-sectional areas were compared between immobilized (right forelimb), contralateral weight bearing (left forelimb), and control forelimbs with Kruskal-Wallis and post hoc tests. At 16 weeks, bone mineral density, cortical load, yield, and stiffness as well as cancellous bone failure stress, yield stress, and modulus were significantly lower (p < 0.02) for immobilized limbs than control limbs. Immobilized limb cancellous bone mechanical properties were 28%-74% of control values, and cortical bone mechanical properties were 71%-98% of control values. After 32 weeks of remobilization, cortical and cancellous bone mechanical properties were not different from control values except that cortical bone failure stress and modulus were significantly higher (p < 0.01) between remobilized and control limbs. In summary, 16 weeks of forelimb immobilization was associated with significantly lower mechanical properties, and with greater differences in cancellous than cortical bone properties. Mechanical properties were not different from control values after 32 weeks of recovery that included 16 weeks of treadmill exercise.

Zoledronate (CGP 42'446), a bisphosphonate, protects against metaphyseal intracortical defects in experimental inflammatory arthritis

This study investigated zoledronate (CGP 42'446), a bisphosphonate, as a potential prophylactic and therapeutic agent against intracortical defects in metaphyseal bone in an experimental model of inflammatory arthritis. Inflammatory arthritis was induced in the right tibiofemoral joint of rabbits by the repeated injection of carrageenan. Three groups of animals were treated with the bisphosphonate daily, beginning at different points after the induction of arthritis. Cross sections of the right distal femoral metaphysis were prepared, and intracortical defects were examined by computerized image analysis. The percentage of total bone area with defects (the ratio of void area to total bone area) was greatly increased in the arthritic group compared with that in the normal group (p < 0.001). In all groups treated with the bisphosphonate, there was a significantly lower percentage of total bone area with defects compared with that in the arthritic group (p < 0.001). Treatment was likewise effective in reducing the zonal (anterior and posterior) predilection for the formation of defects observed in arthritis. Although inflammatory arthritis has a substantial effect in producing intracortical defects in metaphyseal bone, a bisphosphonate, zoledronate, was considerably effective in preventing these changes from occurring.

Etidronate for the Neurotologic Symptoms of Otosclerosis: Preliminary Study

The efficacy of etidronate, a Bisphosphonate, was assessed as a treatment for the inner ear symptoms of otosclerosis in a retrospective case review of 896 patients diagnosed with otosclerosis, with primary complaints of dizziness, hearing loss, tinnitus or Meniere's syndrome. The diagnosis of otosclerosis was based on small-pixel computed tomography of the temporal bones. Of the 896 patients placed on an etidronate protocol, 545 were followed for more than six months and were analyzed. The symptomatic response to etidronate, as well as audiologic and computerized rotary chair results were used in the assessment. Patients who were previously on sodium fluoride were separately analyzed. In this preliminary study etidronate appeared to be an effective treatment for the neurotologic symptoms of otosclerosis. Prospective blinded efficacy studies of the bisphosphonates in the treatment of otosclerosis should be undertaken.

Prevention of bone loss by bisphosphonate YM175 in ovariectomized dogs with dietary calcium restriction

We have evaluated the effects of YM175 (disodium dihydrogen (cycloheptylamino) methylenebisphosphonate monohydrate), a novel bisphosphonate, on bone mineral densities (BMD) at the lumbar spine and forelimb in ovariectomized beagles with dietary calcium restriction. Groups 1 and 2 were given a sham operation and Groups 3-6 were ovariectomized. One month later (month 0), a low calcium diet was given to Groups 2-6. Groups 4-6 were orally treated with YM175 at doses of 0.01, 0.1 and 1.0 mg/kg, respectively, for 18 months. Changes in BMD at the lumbar spine and left forelimb were determined serially by dual energy X-ray absorptiometry. Calcium restriction decreased lumbar BMD by 19% at month 2 and by up to 30% at month 17 compared to its baseline value, but ovariectomy itself had a minimal effect on bone mass in dogs with restricted calcium intake. YM175 (1 mg/kg) prevented the bone loss at month 2 and YM175 at 0.1 mg/kg or more inhibited the BMD reduction at month 17. The magnitude of BMD reduction of the forelimb was less remarkable as compared to that of the lumbar spine. Urinary hydroxyproline excretion and plasma osteocalcin levels were increased by calcium restriction, indicating a high turnover of bone. YM175 reduced hydroxyproline excretion but not osteocalcin levels. These results indicate that YM175 prevents bone loss induced by calcium restriction and ovariectomy through partially normalizing high bone turnover.

In vitro inhibition of membrane-mediated calcification by novel phosphonates

The effects of a series of novel phosphonates on the kinetics of mineral development in an ionophore-primed 7:2:1 phosphatidylcholine (PC): dicetylphosphate (DCP): cholesterol (Chol) liposomal model system are reported. When present at 2.5 micromol/liter or 25 micromol/liter concentrations in the solution surrounding the liposomes, the investigated phosphonates did not significantly delay the initial formation of hydroxyapatite-like calcium phosphate salts (HAP) within the liposomes or the penetration of HAP crystals through the enclosing membranes. However, the phosphonates variably retarded the subsequent growth and proliferation of the HAP crystals once they became directly exposed to the phosphonate-containing solution. The effectiveness of phosphonates in inhibiting extraliposomal precipitation strongly depended on their structure. The inhibitory action on active surface growth sites of released intraliposomal crystals was found to be the most effective if the phosphonate molecule contained two phosphonic groups linked to the same C atom. At a phosphonate concentration of 25 micromol/liter, the following general order of effectiveness was established: geminal bisphosphonate >/= geminal tetrakisphosphonate > bisacylphosphonates > monoacylphosphonate > bisalkylphosphonate. Within the bisacylphosphonate family, the highest inhibitory action was observed when four or five -CH2- groups separated the ketophosphonic groups.

Effect of ovariectomy on bone histology and plasma parameters of bone metabolism in nulliparous and multiparous sows

To investigate the suitability of the pig as animal model for postmenopausal osteoporosis, effects of ovariectomy (OVX) on bone metabolism and histology were studied in two groups of sows (9 months, nulliparous or 35 months, multiparous). A standard diet of about 1.5% calcium (Ca) was fed till sacrifice at either 12 or 20 months post OVX when mineral content and histology were studied in representative bone specimens of proximal tibia, iliac crest and lumbar vertebrae. At 4, 8, 12, and 18 months post OVX, total and bone-specific alkaline phosphatase (APt, APb) calcidiol, calcitriol and parathyroid hormone (PTH) were measured in plasma. In young sows OVX did not significantly affect plasma variables except for calcitriol, which was higher at 4 months post OVX. No significant differences between OVX or control animals were observed in the variables of bone chemical and histological analyses, neither 12 nor 20 months post OVX. In multiparous sows OVX significantly increased PTH plasma concentrations at 8 months post OVX and plasma calcitriol, APt and APb at 12 months post OVX. All effects were moderate and transient. OVX did not significantly affect the variables of bone chemical and histological analyses neither 12 nor 20 months post OVX. Although undoubtedly the clinical-chemical changes observed were not accompanied by any histomorphometric signs of osteopenia/osteoporosis, it must be left to future experiments as to whether this resulted from the ample calcium supply provided. This possibility is supported by recent observations showing that porcine osteopenia could be induced by OVX in animals maintained on only 0.75% dietary calcium but not on higher (0.9%) Ca regimens.