Effect of etidronate on bone in orchidectomized and sciatic neurectomized adult rats

The Effect of Normobaric Intermittent Hypoxia Therapy on Bone in Normal and Disuse Osteopenic Mice

Bromer, Frederik Duch, Mikkel Bo Brent, Michael Pedersen, Jesper Skovhus Thomsen, Annemarie Brüel, and Casper Bindzus Foldager. The effect of normobaric intermittent hypoxia therapy on bone in normal and disuse osteopenic mice. High Alt Med Biol. 22: 225-234, 2021. Background: Systemic intermittent hypoxia therapy (IHT) has been shown to elicit beneficial effects on multiple physiological systems. However, only few studies have investigated the effect of long-term normobaric IHT on bone mass and mechanical and microstructural properties. The aim of the present study was to examine the effect of IHT on bone in both healthy and osteopenic mice. Materials and Methods: Thirty mice were stratified into four groups: Ctrl, Ctrl+IHT, Botox, and Botox+IHT. Osteopenia was induced by injecting Botox into the right hindlimb of the mice causing paralysis and disuse. IHT animals were placed in a normobaric hypoxia-chamber (10% oxygen) for 1 hour twice daily 5 days/week. Animals were sacrificed after 21 days, and DEXA, micro-computed tomography, and mechanical testing were performed on the femora. Results: As expected, Botox resulted in a significant reduction of bone mineral content (-23.4%), area bone mineral density (-19.1%), femoral neck strength (F_max: -54.7%), bone volume fraction (bone volume/tissue volume: -41.8%), and trabecular thickness (-32.4%). IHT had no measurable effect on the bone properties in either healthy or osteopenic mice. Conclusion: The study confirmed that Botox led to loss of bone mass, deterioration of trabecular microstructure, and loss of bone strength. These changes were not influenced by IHT. Notably, IHT had no detrimental effect on bone in either healthy or osteopenic mice. This indicates that IHT of ailments outside of the skeletal system may be administered without causing harm to the bone.

Low-Frequency Electrical Stimulation of Denervated Skeletal Muscle Retards Muscle and Trabecular Bone Loss in Aged Rats

Electrical stimulation (ES)-induced muscle contraction has multiple effects; however, mechano-responsiveness of bone tissue declines with age. Here, we investigated whether daily low-frequency ES-induced muscle contraction treatment reduces muscle and bone loss and ameliorates bone fragility in early-stage disuse musculoskeletal atrophy in aged rats. Twenty-seven-month-old male rats were assigned to age-matched groups comprising the control (CON), sciatic nerve denervation (DN), or DN with direct low-frequency ES (DN+ES) groups. The structural and mechanical properties of the trabecular and cortical bone of the tibiae, and the morphological and functional properties of the tibialis anterior (TA) muscles were assessed one week after DN. ES-induced muscle contraction force mitigated denervation-induced muscle and trabecular bone loss and deterioration of the mechanical properties of the tibia mid-diaphysis, such as the stiffness, but not the maximal load, in aged rats. The TA muscle in the DN+ES group showed significant improvement in the myofiber cross-sectional area and muscle force relative to the DN group. These results suggest that low-frequency ES-induced muscle contraction treatment retards trabecular bone and muscle loss in aged rats in early-stage disuse musculoskeletal atrophy, and has beneficial effects on the functional properties of denervated skeletal muscle.

Electrical Stimulation of Denervated Rat Skeletal Muscle Ameliorates Bone Fragility and Muscle Loss in Early-Stage Disuse Musculoskeletal Atrophy

We tested whether daily muscle electrical stimulation (ES) can ameliorate the decrease in cortical bone strength as well as muscle and bone geometric and material properties in the early stages of disuse musculoskeletal atrophy. 7-week-old male F344 rats were randomly divided into three groups: age-matched control group (Cont); a sciatic denervation group (DN); and a DN + direct electrical stimulation group (DN + ES). Denervated tibialis anterior (TA) muscle in the DN + ES group received ES with 16 mA at 10 Hz for 30 min/day, 6 days/week. Micro CT, the three-point bending test, and immunohistochemistry were used to characterize cortical bone mechanical, structural, and material properties of tibiae. TA muscle in the DN + ES group showed significant improvement in muscle mass and myofiber cross-sectional area relative to the DN group. Maximal load and stiffness of tibiae, bone mineral density estimated by micro CT, and immunoreactivity of DMP1 in the cortical bone tissue were also significantly greater in the DN + ES group than in the DN group. These results suggest that daily ES-induced muscle contraction treatment reduced the decrease in muscle mass and cortical bone strength in early-stage disuse musculoskeletal atrophy and is associated with a beneficial effect on material properties such as mineralization of cortical bone tissue.

Naringin ameliorates bone loss induced by sciatic neurectomy and increases Semaphorin 3A expression in denervated bone

Naringin maintains bone mass in various osteoporosis models, while its effect on bone in disuse osteoporosis has not been reported. The present study explores whether naringin can prevent disuse osteoporosis induced by unilateral sciatic neurectomy (USN) and whether the Semaphorin 3A-induced Wnt/β-catenin signalling pathway is involved in the osteoprotection of naringin. Naringin dose-dependently prevented the deterioration of bone mineral density (BMD), trabecular structure and biomechanical strength in femur due to USN. Naringin increased bone formation but inhibited resorption, as indicated by bone-turnover markers in blood and urine and the histological staining of Osteocalcin (OCN) and tartrate-resistant acid phosphatase (TRAP) in femur. Semaphorin 3A (Sema3A) and active β-catenin protein decreased after USN and could be restored by naringin to the levels of the sham-operated rats. In addition, naringin in vitro promoted the differentiation of osteoblasts and inhibited osteoclastic differentiation. Our studies suggest that the down-regulation of Sema3A and the subsequent inactivation of Wnt/β-catenin signalling may be some of the mechanisms involved in USN-induced osteoporosis. Naringin could increase the expression of Sema3A and the activation of Wnt/β-catenin signalling to prevent disuse osteoporosis induced by denervation. Thus, naringin functions in bone maintenance and could be a promising therapeutic alternative in preventing disuse osteoporosis.

Vertical Trabeculae are Thinned More Than Horizontal Trabeculae in Skeletal-Unloaded Rats

Skeletal unloading results in a rapid thinning of the trabecular bone network, but it is unknown whether vertical and horizontal trabeculae are equally affected. Therefore, the purpose of the present study was to investigate whether horizontal and vertical trabeculae were thinned similarly during skeletal unloading in rats. Fifty-seven 16-week-old female Wistar rats were randomized into six groups: baseline; control 4 weeks; botulinum toxin A (BTX) 4 weeks; control 8 weeks; BTX 8 weeks; and two BTX injections 8 weeks (BTX + BTX8). The BTX animals were injected in the right hind limb with 4 IU BTX at the start of the study, while the BTX + BTX8 were also injected with 2 IU BTX after 4 weeks. The animals were killed after 0, 4, or 8 weeks. The distal femoral metaphyses were μCT scanned, and the strengths of the femoral necks, mid-diaphyses, and distal femoral metaphyses were ascertained. Disuse resulted in a significant loss of BV/TV, thinning of the trabeculae, and decrease in the degree of anisotropy, and in a significant reduced bone strength after both 4 and 8 weeks. The ratio of horizontal to vertical trabecular thickness (Tb.Th.horz/Tb.Th.vert) and the ratio of horizontal to vertical bone volume (BV.horz/BV.vert) were significantly higher in BTX animals than in control animals. In addition, the horizontal and vertical trabecular thickness probability density functions were more similar in BTX animals than in control animals. In conclusion, skeletal unloading decreased BV/TV, Tb.Th, the degree of anisotropy, and mechanical strength, while BV.horz/BV.vert and Tb.Th.horz/Tb.Th.vert were increased. This indicates that the more loaded vertical trabeculae are pronouncedly more thinned than the less loaded supporting horizontal trabeculae during unloading.

Effect of Combined Teriparatide and Monthly Risedronate Therapy on Cancellous Bone Mass in Orchidectomized Rats: A Bone Histomorphometry Study

This study investigated the effects of combined teriparatide (an anabolic agent) and monthly risedronate (an anti-resorptive agent) therapy on cancellous bone mass in orchidectomized (ORX) rats. Fifty 14-week-old male Sprague-Dawley rats were randomized into five groups of ten animals each: sham-operation + vehicle; ORX + vehicle; ORX + risedronate (90 μg/kg subcutaneous, every 4 weeks); ORX + teriparatide (30 μg/kg subcutaneous, three times per week); and ORX + risedronate + teriparatide. After the 12-week experimental period, cancellous bone in the tibial proximal metaphysis was examined by static and dynamic histomorphometric analyses. ORX decreased bone volume per total volume (BV/TV) and trabecular number (Tb.N), and increased trabecular separation (Tb.Sp). Risedronate increased BV/TV and Tb.N above the sham control values, while teriparatide prevented the ORX-induced decrease in BV/TV and increased trabecular width (Tb.Wi) above sham control levels. Risedronate decreased Tb.Sp below control values, while teriparatide prevented the ORX-induced increase in Tb.Sp. The combination of teriparatide and risedronate further increased BV/TV and Tb.N and decreased Tb.Sp as a result of suppression of bone remodeling, compared with teriparatide alone. These results suggest that teriparatide and monthly risedronate exert different effects on cancellous bone structure and thus have additive effects on cancellous bone mass in ORX rats.

Comparison of bone loss induced by ovariectomy and neurectomy in rats analyzed by in vivo micro-CT

We hypothesized that osteoporosis due to estrogen deficiency progresses faster than due to disuse and that at the same amount of bone loss, disuse leads to less favorable bone structure and mechanical properties than estrogen deficiency. Adult rats were either ovariectomized (OVX) (n = 9) or neurectomized (NX) (n = 8). At week 0, 1, 2, 3, and 4, in vivo micro-CT scans were made of the proximal tibia. Segmented CT-scans at weeks 0 and 4 were used to build a 3D voxel-based micro finite element model (FEM). Displacement in the longitudinal direction was prescribed at the proximal end leading to a compression step of 1%. The severe reduction in metaphyseal bone volume fraction was not significantly different between OVX and NX. Epiphyseal bone loss was less severe in both groups, and BV/TV was significantly lower after NX. Trabecular separation and degree of anisotropy in the metaphysis and connectivity and trabecular number in the epiphysis were significantly more deteriorated after NX. FEM-derived stiffness decreased in both groups, but more after NX. Osteoporosis due to estrogen-deficiency progressed overall at a rate similar to osteoporosis due to disuse. At the same amount of induced bone loss, disuse led to more deteriorated bone structure and mechanical properties than estrogen deficiency.

An in vivo magnetic resonance imaging technique for measurement of rat lumbar vertebral body blood perfusion

The technical feasibility of dynamic contrast-enhanced magnetic resonance imaging (MRI) measurement of rat vertebral blood perfusion using a 1.5 T clinical scanner and a small surface coil was investigated in this study. Nine male 7-month-old Wistar-Kyoto rats were used. Computed tomographic assessment of lumbar vertebral bone mineral density (BMD) and MRI assessment of lumbar vertebral blood perfusion were performed twice with 8 weeks' interval. A 4.7 cm surface coil was used for receiving radiofrequency signal. Gadolinium-DOTA (0.3 mmol/kg) was injected through the tail vein of the rat as a quick bolus and dynamic MRI scan was carried out on the central sagittal plane of the lumbar spine for 8 min with a temporal resolution of 0.6 s. Blood perfusion parameters of wash-in rate, maximum enhancement and wash-out rate were derived from the dynamic MR images. No vertebral body size and vertebral BMD difference was detected between the two time points ( P = 0.222 and 0.123, respectively). Wash-in rate was 0.105 (±0.016)% and 0.111 (±0.018)%, maximum enhancement 126.5 (±10.6)% and 129.2 (±13.4)%, and wash-out rate 0.788 (±0.182)% and 0.792 (±0.182)% for the two time points. With these parameters, no difference was found between the two time points with a P value of 0.575, 0.889 and 0.754, respectively. We conclude that dynamic contrast-enhanced MRI measurement of rat vertebral blood perfusion using a 1.5 T clinical scanner and a small surface coil is feasible and reliable. This technique offers a non-invasive means to probe vertebral blood perfusion changes associated with rat disease models.

Beneficial effects of combined administration of alendronate and alfacalcidol on cancellous bone mass of the tibia in orchidectomized rats: a bone histomorphometry study

The purpose of the present study was to examine the effects of combined administration of alendronate (ALN) and alfacalcidol (ALF) on the cancellous and cortical bone mass of the tibia in orchidectomized rats. Fifty male Sprague-Dawley rats, 3 mo of age, were randomized by the stratified weight method into five groups: age-matched control, orchidectomy, and orchidectomy with administration of ALN (2.5 mug/kg, s.c., 5 times a week), ALF (0.05 microg/kg, p.o., 5 times a week), or ALN+ALF. The total experimental period was 12 wk. Orchidectomy reduced the cancellous bone mass of the proximal tibial metaphysis and maturation-related cortical bone gain of the tibial diaphysis as a result of increased trabecular bone resorption and decreased periosteal bone formation and also increased endocortical bone erosion and formation. ALN suppressed trabecular bone resorption and endocortical bone erosion and formation and increased periosteal bone formation, while ALF increased the number of osteoblasts and suppressed trabecular bone resorption and markedly increased periosteal and endocortical bone formation. Thus, both ALN and ALF prevented the orchidectomy-induced reduction in the cancellous bone mass and maturation-related cortical bone gain. Combined administration of ALN and ALF increased the cancellous bone mass as compared with the values observed in age-matched controls by causing more marked suppression of trabecular bone resorption. The present study showed the beneficial effects of combined administration of ALN and ALF on the cancellous bone mass of the tibia in orchidectomized rats.

Orchidectomy models of osteoporosis

Long considered a disease of post-menopausal women, osteoporosis is increasingly being recognized among the growing population of elderly men. Androgen deficiency may be associated with an increase of bone resorption in elderly men and so, with remodeling imbalance and fracture risk. It is firmly established that androgen withdrawal induced by orchidectomy (ORX) results in decreased bone mass in animal models especially in rodents. The mature rat is the model of choice. Skeletal effects of ORX in rats have been studied at the tissular and cellular level. It induces a decrease of BMD and BV/TV with microarchitecture alterations due to an increased bone remodeling. The present chapter focuses on the ORX surgery in rats and mice.

Comparison of dried plum supplementation and intermittent PTH in restoring bone in osteopenic orchidectomized rats

Bone loss was confirmed after 90 days in 50 6-month-old male Sprague Dawley rats that were sham-operated or orchidectomized (ORX). In this study, we have shown that dried plum (DP) has potent effects on bone in terms of bone mass, microarchitecture, and strength in osteopenic male rats. Although these changes may be mediated through the suppression of bone resorption, the fact that the restoration in some of the bone structural and biomechanical parameter shares some similarities with parathyroid hormone (PTH) should not be overlooked. Further investigation is needed on a mechanistic level to clarify the influence of DP on bone metabolism.

INTRODUCTION

This study was designed to investigate the extent to which DP reverses bone loss in osteopenic ORX rats and to compare its effects to PTH.

MATERIALS AND METHODS

Fifty, 6-month-old male Sprague Dawley rats were sham-operated or ORX, and bone loss was confirmed after 90 days. The ORX groups were assigned to control (AIN-93M) diet, 25% DP diet, or PTH (80 microg/kg) for 90 days.

RESULTS

DP induced an 11% increase in vertebral and femoral BMD compared to ORX-controls. BMD in the PTH-treated group was increased by 20.7% (vertebra) and 17.9% (femur). Vertebral trabecular bone volume (BV/TV) and number were increased by DP and trabecular separation was decreased compared to controls, which were similar to PTH. Alterations in trabecular bone of the femur were similar to those in the vertebra, but DP did not restore BV/TV to the same extent. Cortical thickness was improved by DP and further enhanced by PTH. DP tended to decrease urinary deoxypyridinoline and calcium, but did not alter alkaline phosphatase or osteocalcin.

CONCLUSION

We conclude that though the degree of improvement was not equivalent to PTH with regard to all parameters, DP reverses bone loss due to ORX and the mechanisms should be further investigated.

Trabecular bone microarchitecture is related to the number of risk factors and etiology in osteoporotic men

Microarchitecture of trabecular bone is a very important component of bone quality in osteoporosis and a determinant of vertebral fracture in men with low bone mineral density (BMD). In contrast to women, male osteoporosis is, in most cases, secondary. The relationships between microarchitecture and different risk factors have never been evaluated in men. About 152 men with low BMD at the lumbar spine or hip (BMD, T-score < -2.5) were included in this study. Risk factors were: age, BMI, alcohol intake, corticosteroid therapy, hypogonadism, and chronic diseases. Transiliac bone biopsies were obtained and histomorphometry was done on an image analyzer; the following parameters were measured: cortical thickness (Ct.Th), trabecular bone volume (BV/TV), trabecular thickness (Tb.Th), separation (Tb.Sp) and number (Tb.N), interconnectivity Index (ICI), star volume of the bone marrow, and strut analysis with node and free-end count. The 50 men with two risk factors had a lower BMD, lower Ct.Th and a significant higher star volume than those with one factor or idiopathic osteoporosis. The 26 men with at least three risk factors, had a lower BMD, a reduction of BV/TV and Ct.Th and a marked disorganization of the trabecular network (increased Tb.Sp, ICI, star volume, and free-end to free-end struts). The prevalence of vertebral fractures was higher in these patients. When the main risk factor was considered, a marked decrease in trabecular bone connectivity was observed in hypogonadic men. In osteoporotic men, higher the number of risk factors, lower the connectivity of trabecular network and higher the vertebral fracture risk.

Disuse and orchidectomy have additional effects on bone loss in the aged male rat

INTRODUCTION

A severely osteopenic rat model was obtained by combining orchidectomy (ORX) and disuse (due to local paralysis induced by botulinum toxin [BTX] in the quadriceps muscle).

METHODS

Forty-two aged male rats (5-6 months old) were randomized into three groups: 18 were SHAM operated; 6 were ORX; and 18 were ORX and BTX injected in the right hindlimb. One, two, and three months after surgery, bone mass (BV/TV) and microarchitectural parameters (Tb.Th, Tb.N, Tb.Sp, Tb.Pf, and structure model index [SMI]) were measured by microcomputed tomography (microCT) on the primary and secondary spongiosa of the femur. Osteoid parameters (OS/BS, O.Th), the number of osteoclasts (Nb.Oc), and the mineral apposition rate (Ct.MAR, Cn.MAR) were measured by histology. The serum tartrate-resistant acid phosphatase (TRAcP) 5b activity was measured by immunoassay.

RESULTS

ORX induced a decrease of BV/TV, Tb.N and an increase of Tb.Sp, Tb.Pf, and SMI on both primary and secondary spongiosa. ORX and BTX had cumulative effects on bone loss, since differences were maximized on the right femur. The decrease in BV/TV reached -65%. Osteoid parameters and mineral apposition rate increased during the time course of the study. A peak of serum TRAcP was found at 7 days post-ORX. TRAcP levels reached the highest values in the ORX-BTX groups and the effect lasted longer than in the group with ORX alone. The association of ORX-BTX induced a greater bone resorption, due to the removal of complete trabeculae, compared to ORX alone.

CONCLUSION

This model induced a severe and rapid bone loss and can be used to explore pharmacological- and biomaterial-based countermeasures.

Evaluation of an injectable bone substitute (betaTCP/hydroxyapatite/hydroxy-propyl-methyl-cellulose) in severely osteopenic and aged rats

The use of injectable biomaterials is of interest in osteoporotic patients to locally restore bone mass in sites at risk of fracture. An injectable bone substitute (IBS1 made of betaTCP/hydroxyapatite as a calcium phosphate substitute and hydroxy-propyl-methyl-cellulose as a polymer carrier) was used in a severely osteopenic rat model obtained by combining orchidectomy (ORX) and disuse (paralysis induced by botulinum toxin - BTX). Fifty-six aged male rats were randomized into three groups: 18 were SHAM operated; 38 were ORX and BTX injected in the right hindlimb; they constituted the OP (osteoporotic) group. One month after ORX-BTX surgery, 20 of these OP rats received a IBS1 injection in the right femur (OP-IBS1 rats). Animals were studied at the time of IBS1 injection 1 month post ORX-BTX (M1), 1 month (M2) and 2 months (M3) after IBS1 injection. Bone mass (BV/TV) and microarchitectural parameters were measured by microCT. BV/TV was decreased after ORX-BTX; ORX and BTX had cumulative effects on bone loss (differences maximized on the right femur). BV/TV (combining the volume of both bone and material in OP-IBS1 rats) was elevated at M1 but decreased at M2. Marked bone formation was found onto the biomaterial granules but bone had a woven texture. A marked increase in the number of nonosteoclastic TRAcP+ cells was found in the implanted area. IBS1 induced new bone formation shortly after implantation but both IBS1 and woven bone were resorbed without inducing lamellar bone. Biomaterial trials must be conducted with long-term implantation periods, in aged osteoporotic animals.

Dried plum prevents bone loss in a male osteoporosis model via IGF-I and the RANK pathway

Previously, dietary supplementation with dried plums, a rich source of polyphenolic compounds with antioxidant and anti-inflammatory properties, has been shown to improve bone density, microstructure and biomechanics in female animal models of osteopenia. We designed this study to determine the extent to which dried plum prevents skeletal deterioration in gonadal hormone deficient male animals and to begin to understand its mechanism of action. Sixty 6-month-old male Sprague-Dawley rats were either sham-operated (Sham = 1 group) or orchidectomized (ORX = 4 groups) and randomly assigned to dietary treatments: standard semi-purified diet (Control) with either LD = 5%, MD = 15%, or HD = 25% (w/w) dried plum for 90 days. At the end of the treatment period, both the MD and HD dried plum completely prevented the ORX-induced decrease in whole body, femur, and lumbar vertebra bone mineral density (BMD). Biomechanical testing indicated that the MD and HD of dried plum prevented the ORX-induced decrease in ultimate load of the cortical bone as well as the compressive force and stiffness of trabecular bone within the vertebrae. Analyses of trabecular microarchitecture of the distal femur metaphysis and vertebral body revealed that HD dried plum protected against the decrease in trabecular bone volume (BV/TV) induced by ORX. In the distal femur, all doses of dried plum improved trabecular number (TbN) and separation (TbSp) compared to the ORX-control group, while MD and HD dried plum prevented the ORX-induced changes in vertebral TbN and TbSp. At the end of the 90-day treatment, no remarkable changes in serum osteocalcin or alkaline phosphatase in any of the treatment groups were observed, while serum insulin-like growth factor (IGF)-I was increased by dried plum. The ORX-induced increase in urinary deoxypyridinoline (DPD) excretion was completely prevented by all doses of dried plum coinciding with down-regulation of gene expression for receptor activator of NFkappa-B ligand (RANKL) and osteoprotegerin (OPG) in the bone. We conclude that dried plum prevents osteopenia in androgen deficient male rats, and these beneficial effects may be attributed in part to a decrease in osteoclastogenesis via down-regulation of RANKL and stimulation of bone formation mediated by IGF-I.

Three-point bending of rat femur in the mediolateral direction: introduction and validation of a novel biomechanical testing protocol

Mediolateral three-point bending of the rat midfemur was developed to enable the assessment of the mechanical competence of the elliptic bone cross-section in terms of its widest diameter, the apparent primary direction of bone adaptation to loading.

INTRODUCTION

Today, the most commonly used method to characterize the biomechanical properties of appendicular long bones is the three-point bending testing of the midfemur in the anteroposterior (AP) direction. However, as the diameter of the elliptic cross-section of femoral diaphysis is widest in the orthogonal mediolateral (ML) direction, the femoral diaphysis should also show the highest resistance to bending along this direction. The objective of this study was thus to introduce and validate a mechanical testing protocol for femoral midshaft along the ML direction.

MATERIALS AND METHODS

To determine the repeatability of the novel testing protocol, 38 pairs of rat femora underwent a comprehensive structural analysis by pQCT followed by ML three-point bending. For comparison of the repeatability, corresponding tests were performed on the femoral neck. To validate the novel testing direction, the left hindlimb of 24 rats was neurectomized for 6 months, whereas the right limb served as an intact control. After excision, one half of these pairs of femora were randomly subjected to three-point bending test in the conventional AP direction and the remaining in the orthogonal ML direction.

RESULTS

The precision (CVrms) of breaking load, stiffness, and energy absorption of the femoral midshaft in the ML direction was 3.8%, 6.6%, and 14.5%, respectively. The corresponding values for femoral neck compression test were 7.6%, 17.9%, and 18.7%, respectively. The loading-induced effect on the femoral midshaft (difference between the neurectomized [nonloaded] and contralateral intact [loaded] femur) was +2.2%, +1.9%, and +2.1% in the AP direction and -18.9%, -17.6%, and -20.3% in the ML direction (p < 0.01 for all comparisons), respectively.

CONCLUSIONS

Our results show that testing of rat femoral midshaft in the ML direction is a precise and biologically valid method to determine the structural strength of this widely used skeletal site in experimental bone research.

Soy affects trabecular microarchitecture and favorably alters select bone-specific gene expressions in a male rat model of osteoporosis

We have recently reported that soy isoflavones particularly when provided in the context of soy protein are capable of preventing loss of bone mineral density due to orchidectomy in F344 rats. We hypothesize, that soy isoflavones also exert beneficial effects on bone microstructural properties, in part, by enhancing bone formation. Therefore, in the present study, we examined the dose-dependent effects of soy isoflavones on femoral bone microarchitectural properties and select bone-specific gene expressions in the same rat model. Seventy-two, 13-month old rats were either orchidectomized (ORX; 5 groups) or sham-operated (Sham; 1 group) and immediately placed on dietary treatments for 180 days. Four of the ORX groups were fed either casein- or soy protein-based diets each with one of two doses of isoflavones either 600 or 1200 mg/kg diet. Rats in the remaining ORX control and Sham groups were fed a control casein-based diet. Soy protein at the high isoflavone dose, and to a lesser extent with the lower dose, reduced the magnitude of the ORX-induced decreases in trabecular bone volume (BV/TV) and trabecular number (Th.N) and increase in trabecular separation (Tb.Sp) at the femoral neck site. These modulations of trabecular microstructural properties by isoflavones may be due to increased mRNA levels of alkaline phosphatase (ALP), collagen type I (COL), and osteocalcin (OC), which are associated with enhanced bone formation. These findings confirm our earlier observations that the modest bone protective effects of soy isoflavones are due to increased rate of bone formation.

Alcohol-induced bone degradation and its early detection in the alcohol-fed castrated rats

The objective of this study was to examine alcohol-induced changes of bone in hormone-deficient males using the developed method. In the process of bone resorption, type I collagen crosslinking molecules, pyridinoline (PYD), are released into the circulation and cleared by the kidneys. (2)H(2)O as a tracer has been applied to measure the synthesis rates of slow-turnover proteins and successfully applied to bone collagen synthesis in our hormone deficiency rats. This study demonstrated for the first time, the early changes of the femur bone degradation in hormone-deficient male individuals, more influenced by alcohol through histopathological study, serum PYD assay, and (2)H(2)O labeling. We also observed that serum PYD was a sensitive pathological marker of bone degradation in castrated osteoporosis males and the unique features of (2)H(2)O labeling to measure the bone turnover collagen synthesis rates were excellent markers of bone degradation and aging.

Intermittently administered parathyroid hormone 1-34 reverses bone loss and structural impairment in orchiectomized adult rats

Male osteoporosis is emerging as a central theme in bone research. As in females, hypogonadism appears as a principal risk factor in men that leads to bone loss and increased fracture incidence. Intermittently administered parathyroid hormone (PTH) reverses bone loss in sex hormone-deprived women and female animals and increases bone mass in elderly men and normal male animals. This study was carried out to assess whether the PTH anabolic activity is also effective in adult castrated males and to gain insight into the underlying tissue processes. Bilateral orchiectomy (ORX) or sham-ORX was performed in 13-week old rats. Five weeks later, the ORX rats were treated intermittently with human PTH(1-34), 80 microg/kg/day or vehicle for 6 weeks. Femora were evaluated by quantitative micro-computed tomography followed by dynamic histomorphometry. The trabecular bone volume density showed 40% and 56% ORX-induced loss in the distal metaphysis at 6 weeks and 12 weeks post-ORX, respectively. PTH(1-34) induced supraphysiologic recovery of this bone loss (155% recovery) consequent to a vast increase in trabecular thickness (174% over sham-ORX controls) and a partial reversal (62%) of the decrease in trabecular number. As compared with the results in 12-week, orchiectomized vehicle-administered rats, the PTH(1-34) treatment induced a significant decrease in osteoclast number (20%) and twofold increase in bone formation rate. While ORX did not affect the femoral diaphysis, PTH(1-34) induced marked cortical thickening via the stimulation of endosteal mineral appositional rate (154% over ORX rats). These data portray PTH(1-34) as a highly potent bone anabolic agent in adult ORX rats, mainly by increasing both the trabecular and cortical thicknesses through its effect on osteoblasts and osteoclasts. The adult ORX rat is useful for investigating the processes involved in bone anabolic activity in castrated osteoporotic males and for the development of bone anabolic agents for treating this condition.

Effect of Mornidae Radix extracts on experimental osteoporosis in sciatic neurectomized mice

The preventive and therapeutic effects of aqueous extracts of Mornidae Radix (MR) were observed in sciatic neurectomized mice, a disused osteoporotic model. The right hind limbs of 80 mice were neurectomized and 20 mice were sham-operated and served as a sham control. Then 50, 100 and 200 mg/kg of MR extracts were dosed 3 days after neurectomy for 6 weeks in the prevention study and were dosed 2 weeks after neurectomy for 12 weeks for the therapeutic study. After dosing with the MR extracts, the thickness of the hind limbs, tibia failure load, tibia bone mineral density (BMD), serum osteocalcin levels, tibia calcium (Ca) and phosphorus (P) contents were monitored with histomorphometrical changes of the tibia. In both the prevention and therapeutic studies, the MR extracts significantly and dose-dependently suppressed the decrease in hind limb thickness, tibia failure load, BMD, tibia Ca and P contents with an increase in serum osteoclacin levels. In addition, the MR extracts also significantly and dose-dependently suppressed the decrease in histomorphometrical parameters of the tibia such as volume, length and thickness of trabecular bone and thickness of cortical bone with an increase in osteoclast cells in both the prevention and therapeutic studies. Based on these results, the MR extracts may act as both a suppressor of bone resorption and an enhancer of bone formation in vivo and may have some favorable effects for preventing and treating the osteoporosis induced by sciatic neurectomy.

Effects of risedronate on femoral bone mineral density and bone strength in sciatic neurectomized young rats

Immobilization induces a rapid loss of bone density and bone strength in rats. The purpose of the present study was to examine the effects of risedronate (Ris) on the femoral bone density and bone strength of sciatic neurectomized young rats. Forty male Sprague-Dawley rats, 6 weeks of age, were randomized by the stratified weight method into the following four treatment groups of 10 rats each: sham-operation, bilateral sciatic neurectomy (NX), NX + low-dose Ris (0.25 mg/kg/day, orally), and NX + high-dose Ris (0.5 mg/kg/day, orally). After 8 weeks of feeding, the volumetric bone mineral density (vBMD) and stress strain index (SSI) of the femoral distal metaphysis and middiaphysis of the rats were measured by peripheral quantitative computed tomography. The mechanical properties of the femoral distal metaphysis and middiaphysis were measured by the compression and three-point bending tests, respectively. The femoral length was also measured. As compared with the findings in the sham-operated controls, NX resulted in a loss of femoral length, cancellous vBMD, SSI, maximum load, stiffness, and breaking energy of the femoral distal metaphysis; there was also loss of cortical thickness, SSI, maximum load, and stiffness of the femoral middiaphysis, with no significant effects on the cortical vBMD or breaking energy of the femoral middiaphysis. High-dose Ris increased the vBMD to values higher than those in the sham-operated controls, and prevented the loss of SSI, maximum load, and stiffness of the femoral distal metaphysis, while low-dose Ris prevented the loss of cancellous vBMD of the femoral distal metaphysis. Neither high- nor low-dose Ris affected any of the cortical bone parameters of the femoral middiaphysis, except for cortical thickness, or the femoral length. These findings suggest that Ris may prevent immobilization-induced loss of cancellous bone density and bone strength in a dose-dependent manner without interfering with bone growth, but has no apparent effects on the cortical bone in sciatic neurectomized young rats. The results of the present preclinical study should be taken into consideration prior to the commencement of Ris treatment for disabled children.

Differential effect of short-term etidronate treatment on three cancellous bone sites in orchidectomized adult rats

The aim of the present study was to analyze the effects of short-term treatment with the antiresorptive agent, etidronate, on orchidectomized adult rats, via comparison of three cancellous bone sites, the lumbar vertebral body (LVB), proximal tibial metaphysis (PTM), and distal tibial metaphysis (DTM). Thirty-five male Wistar rats, aged 10 months, were randomly divided into four groups: baseline control (BLC, nF10), age-matched sham-operated control (AMC, nF9), orchidectomy (ORX, nF9), and ORXBetidronate treatment (nF7). Etidronate treatment (10 mg/kg, daily subcutaneous injection) was initiated 2 weeks after surgery and was continued for 2 weeks. Four weeks after surgery, the 5th LVB, PTM, and DTM were processed for histomorphometric analysis of cancellous bone (secondary spongiosa). ORX resulted in a decrease in body weight. No significant difference in cancellous bone volume (BV/TV) was found between the BLC and AMC groups at any skeletal site. The cancellous BV/TV loss was attributable to increased eroded surface (ES/BS) with no significant alteration in the mineral apposition rate (MAR), at all skeletal sites and etidronate treatment in ORX rats significantly decreased ES/BS to a level not significantly different from that in the AMC group, resulting in complete prevention of ORX-induced cancellous BV/TV loss. The MAR was markedly decreased in the PTM and LVB, but maintained in the DTM by etidronate treatment. The present study showed that etidronate treatment could completely prevent ORX-induced cancellous bone loss regardless skeletal sites by suppressing bone resorption. In particular, suppression of bone formation in terms of osteoblastic activity by etidronate treatment was not evident only in the DTM

Effect of vitamin K2 on cortical and cancellous bones in orchidectomized and/or sciatic neurectomized rats

We examined the effect of vitamin K2 on cortical and cancellous bones in orchidectomized and/or sciatic neurectomized rats. Ninety male Sprague-Dawley rats, 3 months of age, were randomized by stratified weight method into nine groups with 10 rats in each group: baseline control (BLC), age-matched intact control (IN), IN+vitamin K2 administration (K), orchidectomy (ORX), ORX+K, unilateral sciatic neurectomy (NX), NX+K, ORX+NX (ONX), and ONX+K. Vitamin K2 (menatetrenone) was administered orally twice a week at a dose of 30 mg/kg each. After 10 weeks of feeding, the tibial shaft and proximal tibia were processed for cortical and cancellous bone histomorphometric analyses, respectively. An ORX-induced reduction in maturation-related cortical bone gain and ORX-induced cancellous bone loss were attributable to increased endocortical and trabecular bone turnover, respectively. NX- and ONX-induced reductions in maturation-related cortical bone gain were attributable to decreased periosteal bone formation and increased endocortical bone turnover, while NX- and ONX-induced cancellous bone loss was attributable to increased bone resorption and decreased bone formation. ORX-induced cancellous bone loss was more pronounced when combined with immobilization. Vitamin K2 administration did not significantly alter any parameters in IN rats. Vitamin K2 administration in ORX rats suppressed endocortical bone resorption and trabecular bone turnover, retarding a reduction in maturation-related cortical bone gain and cancellous bone loss. This effect on cancellous bone loss was primarily because of prevention of a reduction of trabecular thickness. Vitamin K2 administration in NX and ONX rats suppressed bone resorption and stimulated bone formation (mineralization), with retardation of a reduction of trabecular thickness without any significant effect on cancellous bone mass, and suppressed endocortical bone resorption, retarding a reduction in maturation-related cortical bone gain. The present study provides evidence indicating that vitamin K2 has the potential to suppress bone resorption or bone turnover and/or stimulate bone formation in vivo in ORX and/or NX rats.

Effects of tower climbing exercise on bone mass, strength, and turnover in orchidectomized growing rats

To determine the effects of a tower climbing exercise on mass, strength, and local turnover of bone, 70 9-wk-old Sprague-Dawley rats were assigned to seven groups: a baseline control and three groups of sham-operated sedentary, orchidectomized (ORX)-sedentary and ORX-exercise rats. Rats voluntarily climbed a 200-cm tower to drink water from a bottle set at the top. At 4 wk, the periosteal bone formation rate (BFR), moment of inertia, bone mineral content, bone mineral density, and bending load at the midfemur were maintained in ORX-exercise rats, whereas these parameters were reduced in ORX-sedentary rats. At 8 wk, the periosteal mineral apposition rate and BFR in ORX-exercise rats were significantly higher, whereas the parameters in ORX-sedentary rats did not differ compared with sham-sedentary rats. In ORX-exercise rats, the trabecular mineralizing surface, BFR, and bone volume of the lumbar vertebrae were maintained at the same levels as those in the sham-sedentary group, whereas the osteoclast surface decreased compared with the ORX-sedentary group. However, the climbing exercise did not affect bone mineral content, bone mineral density, or the compression load of the lumbar vertebrae. These results show that, in the midfemur, the voluntary climbing exercise maintained cortical bone mass and strength by stimulating periosteal bone formation and partially prevented ORX-induced trabecular bone loss, depressing the elevation of turnover. Interestingly, in ORX rats, the climbing exercise had the opposite effect on bone formation at the periosteal femoral cortical bone, where the exercise increased the bone formation compared with vertebral trabecular bone, where the exercise decreased it.