Treatment with a potent cathepsin K inhibitor preserves cortical and trabecular bone mass in ovariectomized monkeys.

The cysteine protease cathepsin K is involved in osteoclast-mediated bone resorption. We evaluated the effect of daily oral dosing of an inhibitor of human cathepsin K (SB-462795 [relacatib]) for 9 months on bone turnover, mass, and architecture in estrogen-deficient cynomolgus monkeys. Ovariectomized animals were treated orally with relacatib at 1, 3, or 10 mg/kg/day, or oral vehicle plus alendronate at 0.05 mg/kg by IV injection once every 2 weeks. The control groups, ovariectomized and sham-ovariectomized animals, received vehicle (all groups n = 20 animals). Samples for biomarker analysis were collected at various times, bone mass changes were evaluated at 6 and 9 months of treatment, and histomorphometric analysis was performed at 9 months. Relacatib significantly reduced urinary N-telopeptide excretion within 1 week of treatment at all dose levels, an effect that was maintained at the highest dose level. At some time points bone formation markers were elevated at the lowest dose of relacatib. Animals treated with relacatib had dose-dependent preservation of areal bone mineral density reaching statistical significance in distal femur. In femur neck there was significant preservation of total volumetric BMD (vBMD) by relacatib. By histomorphometry, relacatib reduced indices of bone resorption and formation at cancellous sites as did alendronate. In cortical bone, osteonal bone formation rate was reduced by alendronate but preserved at low and medium doses of relacatib. Thus, relacatib preserved cortical and cancellous bone mass in ovariectomized monkeys.

Treatment with human parathyroid hormone (1-34) for 18 months increases cancellous bone volume and improves trabecular architecture in ovariectomized cynomolgus monkeys (Macaca fascicularis).

A key feature of postmenopausal osteoporosis is the loss of trabecular bone mass and connectivity. The current study focuses on these parameters in the assessment of long-term (12 and 18 months) parathyroid hormone (PTH) therapy and its withdrawal (6 months) in the ovariectomized cynomolgus monkey (Macaca fascicularis), a well-characterized model for bone changes associated with postmenopausal osteoporosis. We used static and dynamic histomorphometric parameters to assess the amount and architecture of cancellous bone in four clinically important sites for osteoporotic fractures, including the lumbar vertebra, femoral neck, distal radius, and iliac crest. Recombinant human PTH(1-34) was administered daily to two groups for 18 months at 1.0 microg/kg per day (n = 19) and 5.0 microg/kg per day (n = 21). To study the effects of PTH withdrawal, two groups were administered PTH(1-34) daily for 12 months at 1.0 microg/kg per day (n = 20) and 5.0 microg/kg per day (n = 20), followed by daily administration of vehicle for 6 months. Sham-ovariectomized and ovariectomized (ovx) groups each received daily injections of vehicle for 18 months. Treatment with PTH had minimal effects on bone formation rates at the timepoints studied, but markedly increased cancellous bone volume relative to ovx monkeys in iliac crest biopsies at 6 and 15 months, as well as in terminal specimens of lumbar vertebrae, femoral neck, and distal radius after 18 months. At all sites, PTH significantly improved trabecular architecture, as evidenced by increased trabecular number (Tb.N) and decreased trabecular separation (Tb.Sp), with no significant change in trabecular thickness (Tb.Th). The mechanism of these structural changes is suggested by qualitative observations of trabecular tunneling observed in the iliac crest and vertebra. Longitudinal tunneling of thickened individual trabeculae is hypothesized to convert them into multiple trabeculae, resulting in a normalization of Tb.Th, but an increase in Tb.N. A significant positive effect on cancellous bone volume was still apparent after a 3-6 month withdrawal period following 12 months of PTH treatment in the iliac crest, vertebra, and femoral neck. Corresponding increases in Tb.N and decreases in Tb.Sp also remained significant after PTH withdrawal at these three sites. The distal radius was relatively insensitive to PTH treatment or its withdrawal, compared with the other bones. In summary, PTH therapy dramatically improved cancellous bone mass and architecture in both axial and appendicular sites.

Unbiased determination of cytokine localization in bone: colocalization of interleukin-6 with osteoblasts in serial sections from monkey vertebrae.

Few data are available describing the in vivo localization of cytokines in bone. The objective of this study was to describe the histological localization of interleukin-6 (IL-6) relative to osteoblasts (alkaline phosphate [ALP]-positive cells) and osteoclasts (tartrate-resistant acid phosphate [TRAP]-positive cells) in midsagittal, paraffin-embedded serial sections of thoracic 13 (T-13) vertebrae from 49 female cynomolgus monkeys. Serial sections 1 and 4 were immunostained for IL-6, section 2 was histochemically stained for TRAP, and section 3 was immunostained for ALP. Sixteen centrally located fields were measured in the cancellous compartment and grid alignment among sections was verified using image analysis. Using a Merz grid, IL-6 localized to 6% of the bone surface on sections 1 and 4, whereas TRAP localized to 8.5% and ALP to 12% of the bone surface. Colocalization was defined as positive staining within an 80 x 80 microm block in the first serial section that "overlapped" staining in either the corresponding block or its eight surrounding blocks within the second serial section. For each section, 1600 blocks were analyzed. Using Monte Carlo simulations, random colocalization was calculated to determine the statistical significance of experimental colocalizations. Colocalization of approximately 90% between the two IL-6 sections verified staining reproducibility and proper grid alignment among sections. Colocalization of TRAP and ALP was not statistically different from random (p 0.3). As identified using ALP- or TRAP-positive surfaces, there was significant IL-6 colocalization with osteoblasts (p < 0.003), but not with osteoclasts (p 0.3). These in vivo colocalization data support the hypothesis that osteoblasts produce and respond to IL-6.

Magnetic resonance imaging as a screening procedure to avoid arthroscopy for meniscal tears.

The objective of this study was to evaluate the role of magnetic resonance imaging (MRI) as a screening procedure before arthroscopy of meniscal tears. Forty-one knees in 40 patients underwent MRI and arthroscopy. Compared with arthroscopy, the sensitivity, specificity, positive predictive value and negative predictive value for MRI for the nmedial meniscus were 100%, 77%, 71% and 100%, respectively, while the values for the lateral meniscus were 40%, 89%, 33% and 91%, respectively. The overall accuracy for MRI of the medial and lateral menisci combined was 84%. On the basis of the high predictive value of negative MRI, we conclude that MRI is useful to exclude patients from unnecessary arthroscopy.

Daily treatment with human recombinant parathyroid hormone-(1-34), LY333334, for 1 year increases bone mass in ovariectomized monkeys.

PTH stimulates bone formation to increase bone mass and strength in rats and humans. The aim of this study was to determine the skeletal effects of recombinant human PTH-(1-34) [rhPTH-(1-34)] in monkeys, as monkey bone remodeling and structure are similar to those in human bone. Adult female cynomolgus monkeys were divided into sham-vehicle (n = 21), ovariectomized (OVX)-vehicle (n = 20), and OVX groups given daily s.c. injections of rhPTH-(1-34) at 1 (n = 39) or 5 (n = 41) microg/kg for 12 months. Whole body bone mineral content was measured, as was bone mineral density (BMD) in the spine, proximal tibia, midshaft radius, and distal radius. Serum and urine samples were also analyzed. rhPTH-(1-34) treatment did not influence serum ionized Ca levels or urinary Ca excretion, but depressed endogenous PTH while increasing serum calcitriol levels. Compared to that in the OVX group, the higher dose of rhPTH-(1-34) increased spine BMD by 14.3%, whole body bone mineral content by 8.6%, and proximal tibia BMD by 10.8%. Subregion analyses suggested that the anabolic effect of rhPTH-(1-34) on the proximal tibia was primarily in cancellous bone. Similar, but less dramatic, effects on BMD were observed with the lower dose of rhPTH-(1-34). Daily s.c. rhPTH-(1-34) treatment for 1 yr increases BMD in ovariectomized monkeys without inducing sustained hypercalcemia or hypercalciuria.

Effect of treatment for 6 months with human parathyroid hormone (1-34) peptide in ovariectomized cynomolgus monkeys (Macaca fascicularis).

A potential negative side effect of intermittent parathyroid hormone (PTH) therapy to treat osteoporosis is the loss of cortical bone concomitant with increased cancellous bone mass. We addressed this issue by studying the effects of PTH on whole-body, axial, and appendicular bone mass in an animal model with haversian cortical bone remodeling. Ovariectomized, young adult female cynomolgus monkeys were assigned to placebo (n = 9) or PTH groups (n = 10). The PTH group received 10 microg/kg synthetic human PTH(1-34) peptide by subcutaneous injection, 3 days/week for 6 months, and the placebo group received vehicle. Multiple endpoints of bone mass, strength, and turnover in the axial and appendicular skeleton were assessed, including dual-energy X-ray absorptiometry (DEXA), quantitative computed tomography (qCT), analysis of serum (calcium, phosphorus, alkaline phosphatase, osteocalcin, and tartrate-resistant acid phosphatase) and urinary (calcium and creatinine) biomarkers, histomorphometry, and biomechanical testing. Compared with placebo-treated animals, PTH-treated monkeys had no change in whole-body bone mass, but a 6.7% increase in spinal areal bone mineral density (aBMD) was observed. Cortical bone mass measured by qCT at appendicular sites was not affected by PTH treatment, but there were significant increases in cancellous bone mass in the proximal tibia, and a similar trend in the distal radius. Small, transient increases in serum and urinary calcium were observed, but there were no treatment-related effects on other biochemical endpoints. Increased bone formation rate (BFR/BV) in the midradius and midfemur was accompanied by a nonsignificant increase in midfemur porosity. Increased vertebral cancellous bone volume (BV/TV) was associated with greater trabecular and interstitial thickness with no effect on wall thickness. Increases in bone strength were observed in both axial (vertebral maximum stress and load at fracture) and appendicular (femoral neck fracture load) skeleton. Together, these results indicate that PTH therapy in the cynomolgus monkey results in a net gain of spinal and appendicular cancellous bone mass with no adverse effect on cortical bone.

Changes in bone mass and bone biomarkers of cynomolgus monkeys during pregnancy and lactation.

A substantial amount of calcium is transferred from the mother to the fetus and infant during pregnancy and lactation. Involvement of the skeleton in meeting this demand should be reflected in changes in bone mass and turnover. The purpose of the study was to determine the effects of pregnancy, lactation, and recovery on the skeleton in 43 young (prepeak bone mass) female monkeys. Whole body (WBBMC) and lumbar vertebrae 2-4 bone mineral content were determined by dual x-ray absorptiometry at baseline and 1, 4, and 10 months postpartum. Alkaline phosphatase, bone Gla protein, and urinary crosslinks were measured at baseline, during the third trimester, and 1, 4, and 10 months postpartum. Compared to nonpregnant, nonlactating monkeys, pregnant monkeys had similar rates of bone mass gain (nonpregnant, nonlactating WBBMC, 25+/-9 mg/day; pregnant WBBMC, 20+/-14 mg/day). Compared to pregnant monkeys, lactating females had increased bone turnover, as indicated by elevated bone biomarker levels (lactating alkaline phosphatase, 259+/-20 IU/L) and decreased bone mass (lactating WBBMC, -99+/-21 mg/day). Densitometry showed that bone mass gain in the lactating monkeys did not compensate for lactational loss by 10 months postpartum (WBBMC, 6.95+/-9 mg/day). This lack of recovery may have been due to the fact that serum estrogen concentrations were just beginning to return to baseline at 10 months postpartum. In conclusion, the cynomolgus monkey skeleton responds similarly to that of women during pregnancy and lactation. Recovery from lactational bone loss is not complete by 10 months postpartum.

The anesthetic isoflurane decreases ionized calcium and increases parathyroid hormone and osteocalcin in cynomolgus monkeys.

The effects of anesthetics on calcium metabolism in cynomolgus monkeys were studied. Eight adult female cynomolgus monkeys were used in a crossover design. Blood was collected from each of the monkeys at four timepoints: (1) while conscious; (2) following induction of anesthesia with ketamine, ketamine and atropine, isoflurane, or no anesthetic; (3) at 30 min; and (4) 120 min thereafter. Four experiments were performed with a 1 week washout period between sessions, such that each monkey received each treatment. Potassium was lower in anesthetized monkeys than in those that remained conscious. Cortisol, although high, did not differ among anesthetic treatments. Ketamine and ketamine/atropine did not consistently affect ionized calcium or parathyroid hormone (PTH) concentrations. Isoflurane decreased ionized calcium (0.05 mmol/L), and increased PTH and osteocalcin twofold. The serum inorganic fluoride concentration was higher in monkeys anesthetized with isoflurane than with ketamine/atropine, which may partially account for the decrease in ionized calcium with isoflurane. The increases in PTH and osteocalcin are presumably secondary to the decrease in ionized calcium.

Evaluation of a nonhuman primate model to study circadian rhythms of calcium metabolism.

We evaluated primate models for the study of circadian rhythms in calcium and bone metabolism. Blood and urine were collected from two cynomolgus macaques every 4 h for 24 h. Studies were initiated at three different clock times to separate the effects of repeated experimental sampling from circadian effects. Also, samples were collected from seven monkeys at times of expected maxima and minima. Some parameters exhibited the expected circadian rhythm with increases at night (serum total calcium) or in the early morning (urinary collagen cross-links). Others displayed the effects of the experimental procedure, either increasing (urinary creatinine and phosphorus) or decreasing (osteocalcin, urinary calcium) with repeated sampling. Serum phosphorus, cortisol, and type I procollagen were influenced by both clock time and experimental procedures. Alkaline phosphatase and parathyroid hormone did not show any differences with time or sampling. This data is consistent with findings in humans that bone resorption increases at night and that endogenous corticosteroids decrease bone formation. The usefulness of the monkey model is limited by the physiological stress of sample collection in these subjects.

Effects of pregnancy and lactation on bone in cynomolgus macaques: histomorphometric analysis of iliac biopsies.

The effects of pregnancy and lactation on bone histomorphometry have been studied extensively in rats and dogs. However, these models differ greatly in reproductive physiology compared with women. The purpose of this study was to evaluate histomorphometric changes in iliac crest bone biopsies taken from cynomolgus monkeys (Macaca fascicularis), animals similar to women both skeletally and reproductively. After fluorochrome labeling, paired iliac crest bone biopsies were collected and subjected to structural and dynamic histomorphometric analyses during the third trimester and 3 months postpartum in one group (n=16), at 3 and 9 months postpartum in the second group (n=14), and at 4 month intervals in a nonpregnant control group (n=6). Serum was collected at the time of surgery to measure total alkaline phosphatase (ALP), bone gla-protein (BGP), calcium, and estradiol. Trabecular thickness increased significantly between 3 and 9 months postpartum. Bone formation rates did not differ between control and pregnant monkeys, but were significantly increased during lactation (3 months postpartum) and remained elevated at 9 months postpartum. ALP and BGP levels were elevated at 3 months postpartum, compared with levels during pregnancy, and remained elevated at 9 months postpartum. Estradiol concentrations were greatly elevated during pregnancy, dropped below normal nonpregnant levels by 3 months postpartum, and remained suppressed at 9 months postpartum. These results suggest that, during the third trimester, the rate of bone turnover was not altered, but lactational demands for calcium were met in part by increased bone turnover.

Lack of effect of raloxifene on coronary artery atherosclerosis of postmenopausal monkeys.

Raloxifene has been shown to have estrogen agonist effects on bone and cholesterol metabolism while having estrogen antagonist effects on mammary gland and uterus. Reported here are the results of a study to determine whether raloxifene had the estrogen agonist effect of inhibiting coronary artery atherogenesis and to compare its effects with those of traditional conjugated equine estrogens (CEE) treatment. Ovariectomized (surgically postmenopausal) cynomolgus monkeys were fed a moderately atherogenic diet and treated with a placebo, raloxifene (1 mg/kg x day), raloxifene (5 mg/kg x day), or CEE (Premarin) at a dose that mimicked that of 0.625 mg/day in women. The effects of raloxifene on plasma lipid concentrations were generally comparable to those reported in postmenopausal women treated with raloxifene: reductions in low density lipoprotein cholesterol concentrations and no significant effects on high density lipoprotein cholesterol. We found no evidence that raloxifene had an estrogen agonist effect on coronary arteries. Treatment with CEE resulted in about a 70% reduction in coronary artery plaque size relative to that in the placebo group, whereas neither the low nor the high dose of raloxifene had an effect on coronary artery plaque size. The low dose raloxifene group had about 2 times more atherosclerosis and the high dose group had about 3 times more atherosclerosis than the CEE group.

The androgenic anabolic steroid nandrolone decanoate prevents osteopenia and inhibits bone turnover in ovariectomized cynomolgus monkeys.

We examined the effects of nandrolone decanoate (25 mg im every 3 weeks) on bone mass, serum biomarkers, and bone histomorphometric endpoints in 52 female cynomolgus macaques randomized into four treatment groups: (1) sham-ovariectomized (sham); (2) ovariectomized + placebo for 2 years (ovx); (3) ovx + nandrolone decanoate for 2 years (Nan); and (4) ovx + nandrolone decanoate beginning 1 year after ovx (dNan). Serum alkaline phosphatase (ALP), osteocalcin, and tartrate-resistant acid phosphatase (TRAP) were assayed every 3 months, and X-ray densitometry of the lumbar spine was done every 6 months. Fluorochrome-labeled iliac biopsies collected at baseline and 1 year, and lumbar vertebrae and midshaft femur collected at 2 years, were evaluated histomorphometrically. Body weight increased over 50% with administration of nandrolone. After 2 years, ovx animals had lower spinal BMC and BMD than all other groups. Ovx animals also had higher bone turnover rates than all other groups, as indicated by higher levels of the serum and urine biomarkers, and by at least twofold higher label-based bone formation rates in the femur diaphysis and in both cancellous and cortical bone of the ilium and vertebral bodies. Nandrolone-treated animals had similar serum estradiol levels as the sham animals, presumably due to conversion of endogenous or exogenous androgens. The effects of nandrolone on bone in this experiment are consistent with estradiol action and may be attributable to the increased serum estradiol. Despite >50% higher body weight, nandrolone-treated, ovariectomized animals did not have higher bone mass than sham animals.

Short-term effects of growth hormone and insulin-like growth factor I on cancellous bone in rhesus macaque monkeys.

The purpose of our study was to determine the effects of GH and insulin-like growth factor I (IGF-I) administration singly and in combination on vertebral, tibial, and femoral bone in aged female monkeys as well as the various treatment effects on serum hormone levels and osteocalcin gene expression. Twenty-one ovulating female monkeys (rhesus macaque), aged 16-20 yr (5-6 kg), were divided into four groups to receive the following treatment for 7 weeks via Alzet pumps inserted sc: A, eluant (control group); B, recombinant human IGF-I (rhIGF-I; 120 micrograms/kg.day); C) rhGH (100 micrograms/kg.day); D, combination of rhIGF-I (120 micrograms/kg.day) and rhGH (100 micrograms/kg.day). Serum was assayed serially for glucose, IGF-I, GH, and IGF-binding protein-3 levels. All groups received double labeling with calcein. On the day of death, the primates' second lumbar vertebrae, tibiae, and femora were carefully dissected, fixed in 70% ethanol, and subjected to histomorphometric analysis. Ribonucleic acid was extracted from contralateral tibiae for the purpose of osteocalcin gene expression analysis. Serum glucose was unaffected by treatment. Serum GH was significantly elevated in groups C and D, whereas serum IGF-I and IGFBP-3 were only significantly increased in group D. Histomorphometric analysis showed no significant differences or trends for bone volume in any treatment group. Bone formation rate, surface and/or bone volume referent were significantly higher in both groups treated with GH (C and D) in tibia and femur, with a similar trend in vertebrae. The increase in bone formation rate was due mainly to a significant increase in mineral apposition rate, but there was also an increase in tibial mineralizing surface by GH by factorial analysis (P < 0.05). There were significant treatment effects on osteoid surface and osteoclastic surface in femur in the combination treatment group vs. the controls. Osteocalcin gene expression analysis supported an enhanced expression in both groups treated with GH. These findings are consistent with a short term effect of GH to increase bone remodeling and predominantly osteoblastic activity in the appendicular skeleton. In contrast, other than an isolated increase in osteoclastic surface in femoral bone, IGF-I, when administered alone, was unable to significantly influence bone formation or resorption activity in this short term study.

Decreased bone mass and strength in ovariectomized cynomolgus monkeys (Macaca fascicularis).

Agents for prevention or treatment of osteoporosis must now be tested in a large animal species that exhibits bone remodeling. Ovariectomized, nonhuman primates provide one such model, and they consistently develop osteopenia accompanied by high bone turnover rates. The goal of this study was to further characterize this model, and particularly to determine the effect of ovariectomy on bone strength in vertebrae and femoral necks. Longitudinal evaluations of spinal bone mass and serum markers of bone turnover were performed in 19 sham-ovariectomized (SHAM) and 18 ovariectomized (OVX), domestically reared cynomolgus monkeys, aged > 9 years. OVX monkeys lost bone relative to both baseline values and SHAM controls. Serum markers of bone turnover were increased by OVX. After 72 weeks, both vertebral bone compressive strength and femoral neck breaking strength were significantly decreased in OVX animals compared with SHAM. Ovariectomized cynomolgus monkeys, like postmenopausal women, develop accelerated bone loss, increased bone turnover, and reduced bone strength, and provide a suitable large animal model for efficacy studies with agents for prevention or treatment of osteoporosis.

Oral contraceptive treatment inhibits the normal acquisition of bone mineral in skeletally immature young adult female monkeys.

The purpose of the present study was to determine the effects of oral contraceptive therapy on bone density and serum markers of bone metabolism in a prospective, longitudinal study of young adult female cynomolgus monkeys. Two hundred and seven intact cynomolgus monkeys were randomized to two groups, and fed an atherogenic diet containing either no drug (Control) or a triphasic oral contraceptive regimen (Contraceptive). Measurements of bone density were carried out by dual-energy X-ray absorptiometry at 10-month intervals (0, 10, and 20 months) and serum bone biomarkers were determined at 5-month intervals over the 20-month time course. No significant differences in these variables were observed prior to treatment. Both groups of animals gained bone mineral during the study, indicating that peak bone mass had not been reached at baseline. Contraceptive-treated animals gained less spinal (lumbar vertebrae 2-4) bone mineral content and density and less whole-body bone mineral content than Controls over the course of the study. Significant depressive effects of contraceptive treatment on gains in BMC and BMD were observed during each 10-month interval of the study. Bone metabolism was inhibited in the Contraceptive group, as reflected by marked reductions (approximately 40%) in serum osteocalcin and alkaline phosphatase levels along with moderate reductions in serum acid phosphatase and calcium. The results suggest that triphasic oral contraceptive treatment of young adult female monkeys that have not reached peak bone mass inhibits net bone accretion and/or growth by reducing bone metabolism. Thus, prolonged continuous oral contraceptive use in skeletally immature females may lead to a lower peak bone mass--an effect which could increase the risk of fractures in later life.

Osteoarthritis in cynomolgus macaques. III: Effects of age, gender, and subchondral bone thickness on the severity of disease.

Knee joints from cynomolgus monkeys of both genders and a wide range of ages were examined to characterize further the natural history of osteoarthritis (OA) in these animals. The objectives of this study were to characterize better the subchondral bone changes previously noted in this disease, to determine whether the severity of OA in these animals is affected by age or weight, and to determine whether males and females are affected similarly. As had been seen in previous studies, the medial tibial plateau was the most severely affected site. The thickness of the subchondral plate in the medial tibial plateau increased with increasing severity of articular cartilage lesions in both males and females; however, in monkeys with subchondral plate thicknesses less than 400 microns, articular cartilage lesions were essentially absent. Subchondral plate thickness increased with increasing weight in both genders, but females had a higher subchondral plate thickness than males for a given body weight. There was no correlation between bone volume in the proximal tibial epiphysis and articular cartilage lesions of OA. The prevalence and severity of OA in the medial tibial plateau increased with increasing age, but were not affected by gender or weight. Although there was no correlation between articular cartilage lesions and body mass index or weight, the waist/hip circumference ratio and severity of articular cartilage lesions were correlated in the female monkeys. This work provides evidence that thickening of the subchondral bone plate may be more important than the volume of epiphyseal/metaphyseal cancellous bone in determining the biomechanical stresses in the joint and in influencing the development of articular cartilage lesions.

Development of osteopenia in ovariectomized cynomolgus monkeys (Macaca fascicularis).

Spinal osteopenia that is due in part to failure to gain bone has previously been reported in ovariectomized nonhuman primates. In these studies, development of osteopenia over one year was followed by dual-energy x-ray absorptiometry in both domestically-reared and feral ovariectomized (OVX) and sham-ovariectomized (SHAM) cynomolgus monkeys. To promote development of absolute osteopenia, the domestically-reared animals were all older than nine years and were fed a diet containing 0.14% calcium for most of the experimental period. Both SHAM and OVX feral animals fed 0.6% calcium gained bone mass, with significantly lower rates of gain in SHAM monkeys. OVX domestically-reared monkeys lost bone during one year, while SHAM domestically-reared animals showed no significant change from baseline. Thus, relative osteopenia developed in both experiments, but only the domestically-reared animals developed absolute osteopenia. Nonhuman primates are the only animal model shown to develop absolute osteopenia after ovariectomy. These data suggest that absolute osteopenia develops after ovariectomy in monkeys with stable pre-ovariectomy bone mass which are fed a level of calcium comparable to that consumed by American women.

Effect of treatment for 3 months with human parathyroid hormone 1-34 peptide in ovariectomized cynomolgus monkeys (Macaca fascicularis).

Clinical data suggest that PTH may increase cancellous bone mass at the expense of cortical bone in human beings. In this study, the effects of PTH on whole body, axial and appendicular bone mass were studied in an animal model with Haversian cortical bone remodelling. Ovariectomized, young adult, female cynomolgus monkeys were assigned to Placebo (n = 9) or PTH groups (n = 10). The PTH group received 10 micrograms/kg synthetic human PTH(1-34) peptide by SC injection, 3 days/week for 3 months and the Placebo group received vehicle. Spinal and whole body bone mass were measured by DXA, and proximal tibia, distal radius and mid-radius bone mass were measured by quantitative computed tomography (QCT) at baseline and 3 months. Small, transient increases in serum calcium were observed 4 hours after injection with PTH. Compared to placebo-treated animals, PTH-treated monkeys had no change in whole body bone mass, but a 5% increase in spinal bone mineral density. Cortical bone mass measured by QCT at appendicular sites was not affected by PTH treatment, but there were significant increases in cancellous bone mass in the proximal tibia, and a similar trend in distal radius. PTH stimulated dramatic bone gain in the lumbar spine and at appendicular trabecular bone sites during three months' treatment. There was no evidence of cortical bone loss during the same period.