Differences of bone mass and bone structure in osteopenic rat models caused by spinal cord injury and ovariectomy

Chronic intermittent hypobaric hypoxia ameliorates osteoporosis after spinal cord injury through balancing osteoblast and osteoclast activities in rats

Introduction

As a common complication of spinal cord injury (SCI), most SCI patients suffer from osteoporosis. In our previous study, chronic intermittent hypobaric hypoxia (CIHH) could promote bone fracture healing. We speculated that it may act a role in the progression of osteoporosis. The current study purposed to explore the role of CIHH in the osteoporosis triggered by SCI in rats.

Methods

A SCI-induced SCI model was established by completed transection at T9-T10 spinal cord of Wistar rats. One week after SCI, the rats were conducted to CIHH treatment (PB = 404 mmHg, Po2 = 84 mmHg) 6 hours a day for continuously 7 weeks.

Results

The results of X-radiography and Micro-CT assessment demonstrated that compared with sham rats, the areal bone mineral density (BMD), bone volume to tissue volume, volumetric BMD, trabecular thickness, trabecular number, and trabecular connectivity were decreased. Trabecular bone pattern factor, trabecular separation, as well as structure model index were increased at the distal femur and proximal tibia of SCI rats, which were effectively reversed by CIHH treatment. Histomorphometry showed that CIHH treatment increased bone formation of SCI rats, as evidenced by the increased osteoid formation, the decreased number and surface of TRAP-positive osteoclasts. Furthermore, ELISA and real time PCR results showed that the osteoblastogenesis-related biomarkers, such as procollagen type 1 N-terminal propeptide, osteocalcin in serum, as well as ALP and OPG mRNAs in bone tissue were decreased, while the osteoclastogenesis-related biomarkers, including scleorostin in serum and RANKL and TRAP mRNAs in bone tissue were increased in SCI rats. Importantly, the deviations of aforementioned biomarkers were improved by CIHH treatment. Mechanically, the protective effects of CIHH might be at least partly mediated by hypoxia-inducible factor-1 alpha (HIF-1α) signaling pathway.

Conclusion

The present study testified that CIHH treatment ameliorates osteoporosis after SCI by balancing osteoblast and osteoclast activities in rats.

Inflammaging and bone loss in a rat model of spinal cord injury

Spinal cord injury (SCI) results in significant loss of sublesional bone, adding to the comorbidity of SCI with an increased risk of fracture and post-fracture complications. Unfortunately, the effect of SCI on skeletal health is also likely to rise as the average age of SCI has increased and there are well-known negative effects of age on bone. To date, however, the impact of age and age-associated inflammation (inflammaging) on skeletal health after SCI remains largely unknown. To address this, we compared bone parameters in young (3 month) and middle-aged (9 month) male and female rats with a moderate thoracic contusion injury, to age and sex matched sham-operated controls. Skeletal parameters, locomotor function and serum cytokine levels were assessed at both subchronic (30 days) and chronic (180 days) time points post injury. We hypothesized that SCI would lead to a dramatic loss of bone immediately after injury in all SCI-groups, with inflammaging leading to greater loss in middle-aged SCI rats. We also predicted that while younger rats may re-establish bone properties in more chronic phases of SCI, middle-aged rats would not. Supporting these hypothesis, trabecular bone volume was significantly lower in male and young female SCI rats early after injury. Contrary to our hypothesis, however, there was greater loss of trabecular bone volume, relative to age-matched shams, in young compared to middle-aged SCI rats with no effects of SCI on trabecular bone volume in middle-aged female rats. Moreover, despite recovery of weight-supported locomotor activity, bone loss persisted into the chronic phase of injury for the young rats. Bone formation rates were lower in young male SCI rats, regardless of the time since injury, while both young and middle-aged female SCI rats had lower bone formation in the subchronic but not chronic phase of SCI. In middle-aged rats, SCI-induced higher osteoclast surfaces, which also persisted into the chronic phase of SCI in middle-aged females. Neither age nor SCI-induced increases in inflammation seemed to be associated with bone loss. In fact, SCI had more dramatic and persistent effects on bone in male rats, while aging and SCI elevated serum cytokines only in female rats. Overall, this study demonstrates SCI-induced loss of bone and altered bone turnover in male and female rats that persists into the chronic phase post-injury. The sex and age dependent variations in bone turnover and serum cytokines, however, underscore the need to further explore both mechanisms and potential therapeutics in multiple demographics.

Spatiotemporal responses of trabecular and cortical bone to complete spinal cord injury in skeletally mature rats

Objective

Methods

Results

Conclusions

•

Skeletally mature spinal cord transected rats display biphasic bone loss

•

The osteoporosis manifests over slower time scales than in skeletally immature rats.

•

Relevancy for testing efficacy of interventions against SCI-induced osteoporosis.

Effect of Nesfatin-1 on Rat Humerus Mechanical Properties under Quasi-Static and Impact Loading Conditions

The investigations on the response of bone tissue under different loading conditions are important from clinical and engineering points of view. In this paper, the influence of nesfatin-1 administration on rat humerus mechanical properties was analyzed. The classical three-point bending and impact tests were carried out for three rat bone groups: control (SHO), the humerus of animals under the conditions of established osteopenia (OVX), and bones of rats receiving nesfatin-1 after ovariectomy (NES). The experiments proved that the bone strength parameters measured under various mechanical loading conditions increased after the nesfatin-1 administration. The OVX bones were most susceptible to deformation and had the smallest fracture toughness. The SEM images of humerus fracture surface in this group showed that ovariectomized rats had a much looser bone structure compared to the SHO and NES females. Loosening of the bone structure was also confirmed by the densitometric and qualitative EDS analysis, showing a decrease in the OVX bones’ mineral content. The samples of the NES group were characterized by the largest values of maximum force obtained under both quasi-static and impact conditions. The energies absorbed during the impact and the critical energy for fracture (from the three-point bending test) were similar for the SHO and NES groups. Statistically significant differences were observed between the mean F_{i max} values of all analyzed sample groups. The obtained results suggest that the impact test was more sensitive than the classical quasi-static three-point bending one. Hence, F_{i max} could be used as a parameter to predict bone fracture toughness.

Spirulina Enhances Bone Modeling in Growing Male Rats by Regulating Growth-Related Hormones

In recent years, growth hormone deficiency in children has been treated with hormone therapy despite the possible significant side effects. Therefore, it was deemed beneficial to develop functional foods or dietary supplements for safely improving children's growth. Spirulina platensis is known for its high antioxidant, anti-aging, anti-cancer, and immunity-enhancing properties, as well as its high digestibility and high protein content, but little has been reported about its influence on bone development in children with a normal supply of protein. In this study, we evaluated the effects of spirulina on the bone metabolism and antioxidant profiles of three-week-old growing male rats. The animals were divided into four groups (n = 17 per group) and were fed AIN93G diets with 0% (control), 30% (SP30), 50% (SP50), and 70% (SP70) of casein protein replaced by spirulina, respectively, for seven weeks. We observed that spirulina enhanced bone growth and bone strength by stimulating parathyroid hormone and growth hormone activities, as well its increased antioxidant activity. These results indicate that spirulina provides a suitable dietary supplement and alternative protein source with antioxidant benefits for growth improvement in early developmental stages.

Effect of Periapical Diseases in Development of MRONJ in Immunocompromised Mouse Model

Objectives

This study aimed to assess the effect of zoledronic acid on an immunocompromised mice model with periapical disease.

Materials and Methods

Thirty C57BL/6N mice were randomly divided into three groups (N = 10). All animals were subjected to bilateral ovariectomy (OVX) and then treated with saline (Veh), zoledronic acid (ZA), or concomitant zoledronic acid and dexamethasone (ZA/Dx) for 12 weeks. Eight weeks after starting drug administration, pulpal exposure was conducted on the lower left first molar. Four weeks after pulpal exposure, all mice were sacrificed and the mandibles were collected for radiological and histological examinations.

Results

Microcomputed tomography (μ-CT) examination showed significantly reduced periapical bone resorption in the ZA/Dx group and decreased periodontal bone resorption in both ZA and ZA/Dx groups. Higher bone mineral density (BMD) and strengthened microstructure were found in ZA and ZA/Dx groups. More empty lacunae were found in ZA and ZA/Dx groups.

Conclusions

Apical periodontitis aggravates MRONJ under immunocompromised circumstances. Concurrent use of ZA and steroids inhibits alveolar bone resorption but increases the risk of developing MRONJ.

Black Rice (Oryza sativa L.) Fermented with Lactobacillus casei Attenuates Osteoclastogenesis and Ovariectomy-Induced Osteoporosis

The aim of the present study was to investigate the antiosteoclastogenic effects of black rice (Oryza sativa L.) fermented with Lactobacillus casei (LAB) in RANKL-induced RAW macrophage cells and its antiosteoporosis activity against ovariectomy-induced osteoporosis in rats. LAB extract (LABE) treatment attenuated receptor activator of nuclear factor-kappa B (NF-κB) ligand-induced osteoclastic differentiation in RAW cells by inhibiting intercellular reactive oxygen species generation and downregulating the activation of mitogen-activated protein kinases and NF-κB, leading to the downregulation of c-Fos and expression of nuclear factor of activated T cells c1. This consequently suppressed the expression of osteoclast-specific genes including those for cathepsin K, tartrate-resistant acid phosphatase, calcitonin receptor, and integrin β3. Oral administration of LABE protected against ovariectomy-induced bone loss by significantly inhibiting bone architecture alterations and improving serum bone turnover markers in ovariectomized rats. The findings suggest that the antiosteoporotic activity of LABE may be derived from its antiosteoclastic and anti-bone-resorptive activities. LABE has potential as a promising functional material or substrate to prepare protective agents for osteoporosis and osteoclast-mediated bone diseases.

Longitudinal Examination of Bone Loss in Male Rats After Moderate-Severe Contusion Spinal Cord Injury

To elucidate mechanisms of bone loss after spinal cord injury (SCI), we evaluated the time-course of cancellous and cortical bone microarchitectural deterioration via microcomputed tomography, measured histomorphometric and circulating bone turnover indices, and characterized the development of whole bone mechanical deficits in a clinically relevant experimental SCI model. 16-weeks-old male Sprague-Dawley rats received T₉ laminectomy (SHAM, n = 50) or moderate-severe contusion SCI (n = 52). Outcomes were assessed at 2-weeks, 1-month, 2-months, and 3-months post-surgery. SCI produced immediate sublesional paralysis and persistent hindlimb locomotor impairment. Higher circulating tartrate-resistant acid phosphatase 5b (bone resorption marker) and lower osteoblast bone surface and histomorphometric cancellous bone formation indices were present in SCI animals at 2-weeks post-surgery, suggesting uncoupled cancellous bone turnover. Distal femoral and proximal tibial cancellous bone volume, trabecular thickness, and trabecular number were markedly lower after SCI, with the residual cancellous network exhibiting less trabecular connectivity. Periosteal bone formation indices were lower at 2-weeks and 1-month post-SCI, preceding femoral cortical bone loss and the development of bone mechanical deficits at the distal femur and femoral diaphysis. SCI animals also exhibited lower serum testosterone than SHAM, until 2-months post-surgery, and lower serum leptin throughout. Our moderate-severe contusion SCI model displayed rapid cancellous bone deterioration and more gradual cortical bone loss and development of whole bone mechanical deficits, which likely resulted from a temporal uncoupling of bone turnover, similar to the sequalae observed in the motor-complete SCI population. Low testosterone and/or leptin may contribute to the molecular mechanisms underlying bone deterioration after SCI.

Cannabidiol administration reduces sublesional cancellous bone loss in rats with severe spinal cord injury

Patients with spinal cord injury (SCI) undergo severe loss of bone mineral below the level of lesion, and data on available treatment options after SCI is scarce. The aim of this work was to investigate the therapeutic effect of cannabidiol (CBD), a non-psychoactive cannabis, on sublesional bone loss in a rat model of SCI. The adult male rats were exposed to surgical transection of the cord and treated with CBD for consecutive 14 days. It was found that CBD treatment elevated the serum levels of osteocalcin, reduced the serum levels of collagen type I cross-linked C-telopeptide, and enhanced bone mineral density of tibiae and femurs. Treatment of SCI rats with CBD enhanced bone volume, trabecular thickness, and trabecular number, and reduced trabecular separation in proximal tibiae, and increased ultimate compressive load, stiffness, and energy to max force of femoral diaphysis. Treatment of SCI rats with CBD upregulated mRNA expression of alkaline phosphatase and osteoprotegerin and downregulated mRNA expression of receptor activator of NF-κB ligand and tartrate-resistant acid phosphatase in femurs. Furthermore, treatment of SCI rats with CBD enhanced mRNA expression of wnt3a, Lrp5 and ctnnb1 in femurs. In conclusion, CBD administration attenuated SCI-induced sublesional cancellous bone loss.

Selective protein depletion impairs bone growth and causes liver fatty infiltration in female rats: prevention by Spirulina alga

Chronic protein malnutrition leads to child mortality in developing countries. Spirulina alga (Spi), being rich in protein and growing easily, is a good candidate as supplementation. We showed that Spi completely prevents bone growth retardation and liver disturbances observed in young rats fed a low protein diet. This supports Spi as a useful source of vegetable protein to fight against protein malnutrition.

INTRODUCTION

Chronic malnutrition is a main factor of child mortality in developing countries. A low protein diet impairs whole-body growth and leads to fatty liver in growing rats. Spi has great potential as a supplementation as it has a 60 % protein content and all essential amino acids. However, its specific impact on bone growth and the related secretion of hepatokines have not yet been studied.

METHODS

To address this question, 6-week-old female rats were fed isocaloric diets containing 10 % casein, 5 % casein, or 5 % casein + 5 % protein from Spi during 9 weeks. Changes in tibia geometry, microarchitecture, BMC, BMD, and biomechanical properties were analyzed. Serum IGF-I, FGF21, follistatin, and activin A were assessed as well as their hepatic gene expressions in addition to those of Sirt1, Ghr, and Igf1r. Hepatic fat content was also assessed.

RESULTS

A low protein diet altered bone geometry and reduced proximal tibia BMD and trabecular bone volume. In addition, it increased hepatic fat content and led to hepatic GH resistance by decreasing serum IGF-I and increasing serum FGF21 without altering serum activin A and follistatin. Spi prevented low protein diet-induced bone, hepatic, and hormonal changes, and even led to higher biomechanical properties and lower hepatic fat content in association with specific InhbA and Follistatin expression changes vs. the 10 % casein group.

CONCLUSIONS

Altogether our results demonstrate the preventive impact of Spi on bone growth delay and hepatic GH resistance in conditions of isocaloric dietary protein deficiency.

Inhibition of substance P signaling aggravates the bone loss in ovariectomy-induced osteoporosis

INTRODUCTION

Substance P signaling regulates the functions of both osteoblast and osteoclast. Available reports on the effects of substance P on bone mass are contradictory. The objective of this study was to determine the change of substance P expression in the osteoporotic bone of OVX mice. The effects of substance P signaling blockade by using its specific receptor antagonist L-703606 on bone remodeling in sham-operated mice and OVX mice were also investigated.

METHODS

Forty-eight nine-week-old female C57BL/6J mice were evenly distributed into three groups with sham surgery, OVX or OVX with estrogen replacement. Substance P expression in the bones of each group of mice was evaluated by immunohistochemistry and enzyme immunoassay. Another thirty-two nine-week-old female C57BL/6J mice were divided into a SHAM group (sham surgery followed by vehicle treatment with DMSO), a SHAM + L group (sham surgery followed by 15 mg/kg/d L-703606 repeated intraperitoneal injections), an OVX group (ovariectomy with the same vehicle treatment) and an OVX + L group (ovariectomy with the same L-703606 injections), with 8 mice in each group. Treatment started 3 weeks after surgery and last for 3 weeks. A 2 × 2 factorial experimental design was used to detect the effects of substance P signaling blockade on bone remodeling in sham-operated mice and OVX mice. Techniques including micro-computed tomography, biomechanical testing, histomorphometric analysis, enzyme immunoassay, and real-time PCR were employed.

RESULTS

Immunohistochemistry and enzyme immunoassay revealed that substance P expression significantly decreased in the bones of OVX mice both at 3 weeks and 6 weeks after surgery. Micro-CT tomography demonstrated that application of L-703606 led to bone loss in sham-operated mice, and aggravated the micro-structural deterioration of bones in OVX mice. This was shown by reduced BV/TV (Mean bone volume fraction), Tb.N (Mean trabecular number) and Tb.Th (Mean trabecular thickness), and increased Tb.Sp (Mean trabecular separation). Biomechanical analysis demonstrated that blockade of substance P signaling reduced the maximum stress and maximum load of L3 vertebrae and tibiae. Inhibited recruitment of bone mesenchymal stem cells (BMSCs) to bone remodeling sites, which was evidenced by increased number of osteoclasts, decreased number of osteoblasts and increased osteoid volume in the secondary spongiosa, was observed in the mice treated with L-703606. A significant decrease of OPG/RANKL ratio was also found in the bones of mice treated with L-703606. Body weight, uterine weight and serum estradiol level were not significantly different between the mice treated with L-703606 and those treated with vehicle.

CONCLUSION

The results demonstrated that blocking substance P signaling led to bone loss in sham-operated mice, and exacerbated the bone loss in OVX mice. Substance P signaling had an important role in the maintenance of bone mass.

Sclerostin inhibition prevents spinal cord injury-induced cancellous bone loss

Spinal cord injury (SCI) results in rapid and extensive sublesional bone loss. Sclerostin, an osteocyte-derived glycoprotein that negatively regulates intraskeletal Wnt signaling, is elevated after SCI and may represent a mechanism underlying this excessive bone loss. However, it remains unknown whether pharmacologic sclerostin inhibition ameliorates bone loss subsequent to SCI. Our primary purposes were to determine whether a sclerostin antibody (Scl-Ab) prevents hindlimb cancellous bone loss in a rodent SCI model and to compare the effects of a Scl-Ab to that of testosterone-enanthate (TE), an agent that we have previously shown prevents SCI-induced bone loss. Fifty-five (n = 11-19/group) skeletally mature male Sprague-Dawley rats were randomized to receive: (A) SHAM surgery (T8 laminectomy), (B) moderate-severe (250 kilodyne) SCI, (C) 250 kilodyne SCI + TE (7.0 mg/wk, im), or (D) 250 kilodyne SCI + Scl-Ab (25 mg/kg, twice weekly, sc) for 3 weeks. Twenty-one days post-injury, SCI animals exhibited reduced hindlimb cancellous bone volume at the proximal tibia (via μCT and histomorphometry) and distal femur (via μCT), characterized by reduced trabecular number and thickness. SCI also reduced trabecular connectivity and platelike trabecular structures, indicating diminished structural integrity of the remaining cancellous network, and produced deficits in cortical bone (femoral diaphysis) strength. Scl-Ab and TE both prevented SCI-induced cancellous bone loss, albeit via differing mechanisms. Specifically, Scl-Ab increased osteoblast surface and bone formation, indicating direct bone anabolic effects, whereas TE reduced osteoclast surface with minimal effect on bone formation, indicating antiresorptive effects. The deleterious microarchitectural alterations in the trabecular network were also prevented in SCI + Scl-Ab and SCI + TE animals, whereas only Scl-Ab completely prevented the reduction in cortical bone strength. Our findings provide the first evidence indicating that sclerostin inhibition represents a viable treatment to prevent SCI-induced cancellous and cortical bone deficits and provides preliminary rationale for future clinical trials focused on evaluating whether Scl-Ab prevents osteoporosis in the SCI population.

Testosterone dose dependently prevents bone and muscle loss in rodents after spinal cord injury

Androgen administration protects against musculoskeletal deficits in models of sex-steroid deficiency and injury/disuse. It remains unknown, however, whether testosterone prevents bone loss accompanying spinal cord injury (SCI), a condition that results in a near universal occurrence of osteoporosis. Our primary purpose was to determine whether testosterone-enanthate (TE) attenuates hindlimb bone loss in a rodent moderate/severe contusion SCI model. Forty (n=10/group), 14 week old male Sprague-Dawley rats were randomized to receive: (1) Sham surgery (T9 laminectomy), (2) moderate/severe (250 kdyne) SCI, (3) SCI+Low-dose TE (2.0 mg/week), or (4) SCI+High-dose TE (7.0 mg/week). Twenty-one days post-injury, SCI animals exhibited a 77-85% reduction in hindlimb cancellous bone volume at the distal femur (measured via μCT) and proximal tibia (measured via histomorphometry), characterized by a >70% reduction in trabecular number, 13-27% reduction in trabecular thickness, and increased trabecular separation. A 57% reduction in cancellous volumetric bone mineral density (vBMD) at the distal femur and a 20% reduction in vBMD at the femoral neck were also observed. TE dose dependently prevented hindlimb bone loss after SCI, with high-dose TE fully preserving cancellous bone structural characteristics and vBMD at all skeletal sites examined. Animals receiving SCI also exhibited a 35% reduction in hindlimb weight bearing (triceps surae) muscle mass and a 22% reduction in sublesional non-weight bearing (levator ani/bulbocavernosus [LABC]) muscle mass, and reduced prostate mass. Both TE doses fully preserved LABC mass, while only high-dose TE ameliorated hindlimb muscle losses. TE also dose dependently increased prostate mass. Our findings provide the first evidence indicating that high-dose TE fully prevents hindlimb cancellous bone loss and concomitantly ameliorates muscle loss after SCI, while low-dose TE produces much less profound musculoskeletal benefit. Testosterone-induced prostate enlargement, however, represents a potential barrier to the clinical implementation of high-dose TE as a means of preserving musculoskeletal tissue after SCI.

The antiosteoporotic effects of Cheonggukjang containing vitamin k2 (menaquinone-7) in ovariectomized rats

The effect of dietary vitamin K2 (menaquinone-7, MK-7) and cheonggukjang (CGJ) on the prevention of ovariectomy (OVX)-induced bone loss was studied in rats. Female Sprague-Dawley rats were divided into eight groups: sham-operated; OVX control; OVX treated with MK-7 at doses of 2, 4, and 8 μg/day; and OVX treated with CGJ at doses of 0.063, 0.125, and 0.250 g/day referenced to MK-7 levels at 2, 4, and 8 μg/day, respectively. After 8 weeks of treatment, the preventive effects of MK-7 and CGJ were evaluated by measuring body weights, serum levels of bone turnover markers, bone mineral content (BMC), bone mineral density (BMD), trabecular microarchitectural properties, and bone histological characteristics. Our results showed that rats treated with a high dose of MK-7 (8 μg/day) exhibited a minor inhibitory effect on OVX-induced bone loss, as indicated by a significant increase in trabecular number, as well as BMC and BMD (P<.01). Moreover, the preventive effects of MK-7 were augmented by administration of CGJ at the same MK-7 dose. In addition, the preventive effects of CGJ were shown to be dose dependent, with the highest dose (0.250 g/day) significantly (P<.01) increasing BMC and BMD by 31.8% and 47.6%, respectively. In summary, these results suggest that administration of CGJ containing abundant levels of MK-7 may be a promising approach for the treatment and prevention of osteoporosis.

Anatomic changes in the macroscopic morphology and microarchitecture of denervated long bone tissue after spinal cord injury in rats

To study the effects of mechanical loading on bones after SCI, we assessed macro- and microscopic anatomy in rats submitted to passive standing (PS) and electrical stimulation (ES). The study design was based on two main groups of juvenile male Wistar rats with SCI: one was followed for 33 days with therapies starting at day 3 and the other was followed for 63 days with therapies starting at day 33. Both groups were composed of four subgroups (n = 10/group): (1) Sham, (2) SCI, (3) SCI + PS, and (4) SCI + ES. Rehabilitation protocol consisted of a 20-minute session, 3x/wk for 30 days. The animals were sequentially weighed and euthanized. The femur and tibia were assessed macroscopically and microscopically by scanning electronic microscopy (SEM). The SCI rats gained less weight than Sham-operated animals. Significant reduction of bone mass and periosteal radii was observed in the SCI rats, whereas PS and ES efficiently improved the macroscopic parameters. The SEM images showed less and thin trabecular bone in SCI rats. PS and ES efficiently ameliorated the bone microarchitecture deterioration by thickening and increasing the trabeculae. Based on the detrimental changes in bone tissue following SCI, the mechanical loading through weight bearing and muscle contraction may decrease the bone loss and restore the macro- and microanatomy.

Blockade of substance P receptor attenuates osteoporotic pain, but not bone loss, in ovariectomized mice

OBJECTIVE

The aim of this study was to investigate the effect of a substance P (SP) receptor (NK1 receptor [NK1-R]) antagonist on hyperalgesia and bone metabolism in ovariectomized mice.

METHODS

Thirty-six 9-week-old mice were subjected to either bilateral ovariectomy or sham surgery. Three weeks after the operation, the mice were treated with either a single-dose injection or 2-week repeated daily administration of L-703606, an NK1-R antagonist. Behavioral tests were performed for pain assessment; tibiae and the third lumbar vertebrae were dissected and assessed for microarchitectural or biomechanical properties. The expressions of SP and NK1-R in the dorsal root ganglia and spinal cord were also evaluated.

RESULTS

Both single-dose injection and 2-week repeated injections of L-703606 led to a significant increase in nociceptive threshold in ovariectomized mice. However, the antihyperalgesic effect faded at 2 hours and almost disappeared at 5 hours after a single-dose injection. With the 14-day repeated treatment of ovariectomized mice, the effect was not detectable at 24 hours after the first injection but was obvious at 24 hours after 1-week and 2-week administrations and still existed at 48 hours after the last injection. Ovariectomized mice at the hyperalgesic state had enhanced SP immunoreactivity in the dorsal root ganglia and up-regulated SP and NK1-R expressions in the spinal cord. However, no significant change in serum SP level was detected. Two-week treatment with L-703606 could down-regulate these expressions but failed to salvage the deteriorated trabecular microstructure and reduced compressive strength in ovariectomized mice.

CONCLUSIONS

Estrogen deficiency-induced hyperalgesia is achieved through up-regulation of SP and NK1-R expressions. Blockade of SP receptor can alleviate pain but cannot ameliorate bone loss. NK1-R antagonist is not recommended for the treatment of estrogen deficiency osteoporosis.

Changes to volumetric bone mineral density and bone strength after stroke: a prospective study

RATIONALE AND AIM

Stroke survivors experience accelerated bone loss and increased fracture risk, particularly in paretic weight bearing limbs. Understanding how these changes unfold and their relationship to stroke severity and physical activity could help in the development of targeted interventions to prevent or reduce the severity of these outcomes. The primary aim of this study is to investigate the time course and magnitude of changes in volumetric bone mineral density within the first year after stroke, and to examine relationships with physical activity and motor recovery.

DESIGN

This is a prospective, observational study of 43 nondiabetic, nonambulant adults with first ever hemispheric stroke.

PRIMARY OUTCOME

The primary outcome was the difference in six-month change of total volumetric bone mineral density between paretic and nonparetic distal tibiae, measured at 7% of bone length site using high-resolution peripheral quantitative computed tomography.

SECONDARY OUTCOMES

The secondary outcomes are cortical and trabecular volumetric bone mineral density, cortical thickness, and total and cross-sectional areas of distal tibiae and radii of paretic and nonparetic limbs. Also included are total body and regional bone mineral density derived using dual-energy X-ray absorptiometry, physical activity measured using accelerometry, and motor recovery (Chedoke McMaster Stroke Assessment).

DISCUSSION

Measuring the timing and magnitude of changes to volumetric bone mineral density and bone structure from immediately after stroke, and relationships between these changes with physical activity and motor recovery will provide the basis for targeted interventions to reduce fracture risk in stroke survivors.

Metaphyseal and diaphyseal bone loss in the tibia following transient muscle paralysis are spatiotemporally distinct resorption events

When the skeleton is catabolically challenged, there is great variability in the timing and extent of bone resorption observed at cancellous and cortical bone sites. It remains unclear whether this resorptive heterogeneity, which is often evident within a single bone, arises from increased permissiveness of specific sites to bone resorption or localized resorptive events of varied robustness. To explore this question, we used the mouse model of calf paralysis induced bone loss, which results in metaphyseal and diaphyseal bone resorption of different timing and magnitude. Given this phenotypic pattern of resorption, we hypothesized that bone loss in the proximal tibia metaphysis and diaphysis occurs through resorption events that are spatially and temporally distinct. To test this hypothesis, we undertook three complimentary in vivo/μCT imaging studies. Specifically, we defined spatiotemporal variations in endocortical bone resorption during the 3weeks following calf paralysis, applied a novel image registration approach to determine the location where bone resorption initiates within the proximal tibia metaphysis, and explored the role of varied basal osteoclast activity on the magnitude of bone loss initiation in the metaphysis using μCT based bone resorption parameters. A differential response of metaphyseal and diaphyseal bone resorption was observed throughout each study. Acute endocortical bone loss following muscle paralysis occurred almost exclusively within the metaphyseal compartment (96.5% of total endocortical bone loss within 6days). Using our trabecular image registration approach, we further resolved the initiation of metaphyseal bone loss to a focused region of significant basal osteoclast function (0.03mm(3)) adjacent to the growth plate. This correlative observation of paralysis induced bone loss mediated by basal growth plate cell dynamics was supported by the acute metaphyseal osteoclastic response of 5-week vs. 13-month-old mice. Specifically, μCT based bone resorption rates normalized to initial trabecular surface (BRRBS) were 3.7-fold greater in young vs. aged mice (2.27±0.27μm(3)/μm(2)/day vs. 0.60±0.44μm(3)/μm(2)/day). In contrast to the focused bone loss initiation in the metaphysis, diaphyseal bone loss initiated homogeneously throughout the long axis of the tibia predominantly in the second week following paralysis (81.3% of diaphyseal endocortical expansion between days 6 and 13). The timing and homogenous nature are consistent with de novo osteoclastogenesis mediating the diaphyseal resorption. Taken together, our data suggests that tibial metaphyseal and diaphyseal bone loss induced by transient calf paralysis are spatially and temporally discrete events. In a broader context, these findings are an essential first step toward clarifying the timing and origins of multiple resorptive events that would require targeting to fully inhibit bone loss following neuromuscular trauma.

Difference in intraosseous blood vessel volume and number in osteoporotic model mice induced by spinal cord injury and sciatic nerve resection

In the present study, we examined intraosseous blood vessel parameters of the tibial metaphysis in mice using microcomputed tomography (µCT) to investigate the relationship between post-nerve-injury osteoporosis and local intraosseous blood vessel volume and number. Mice were randomly divided into groups receiving spinal cord injury (SCI), sciatic nerve resection group (NX), or intact controls (30 mice/group). Four weeks after surgery, mice were perfused with silicone and the distribution of intraosseous blood vessels analyzed by μCT. The bone density, μCT microstructure, biomechanical properties, and the immunohistochemical and biochemical indicators of angiogenesis were also measured. The SCI group showed significantly reduced tibial metaphysis bone density, μCT bone microstructure, tibial biomechanical properties, indicators of angiogenesis, and intraosseous blood vessel parameters compared to the NX group. Furthermore, the spinal cord-injured mice exhibited significantly decreased intraosseous blood vessel volume and number during the development of osteoporosis. In conclusion, these data suggest that decreased intraosseous blood vessel volume and number may play an important role in the development of post-nerve-injury osteoporosis.

Bone loss following spinal cord injury in a rat model

The current study was undertaken to follow the time course of bone loss in the proximal tibia of rats over several weeks following thoracic contusion spinal cord injury (SCI) of varying severity. It was hypothesized that bone loss would be more pronounced in the more severely injured animals, and that hindlimb weight bearing would help prevent bone loss. Twenty-six female Sprague-Dawley rats (200-225 g, 6-7 weeks old) received standard thoracic (T9) injuries at energies of 6.25, 12.5, 25, or 50 g-cm. The rats were scored weekly for hindlimb function during locomotion. At 0, 2 or 3, and 8 weeks, high-resolution micro-CT images of each right tibia were obtained. Mechanical indentation testing was done to measure the compressive strength of the cancellous bone structure. The 6.25 g-cm group showed near normal locomotion, the 12.5 and 25 g-cm groups showed the ability to frequently or occasionally generate weight-supported plantar steps, respectively, and the 50 g-cm group showed only movement without weight-supported plantar stepping. The 6.25, 12.5 and 25 g-cm groups remained at the same level of bone volume fraction (cancBV/TV=0.24±0.07), while the 50 g-cm group experienced severe bone loss (67%), resulting in significantly lower (p<0.05) bone volume fraction (cancBV/TV=0.11±0.05) at 8 weeks. Proximal tibia cancellous bone strength was reduced by approximately 50% in these severely injured rats. Instead of a linear proportionality between injury severity and bone loss, there appears to be a distinct functional threshold, marked by occasional weight-supported stepping, above which bone loss does not occur.

Characterization of Salvia miltiorrhiza ethanol extract as an anti-osteoporotic agent

BACKGROUND

Salvia miltiorrhiza (SM) has long been used as a traditional oriental medicine for cardiovascular disease. Accumulating evidence also indicates that SM has anti-osteoporotic effects. This study was conducted to examine the SM-induced anti-osteoporotic effect and its possible mechanisms with various doses of SM.

METHODS

We studied Sprague-Dawley female rats aged 12 weeks, divided into six groups: sham-operated control (SHAM), OVX rats supplemented with SM (1, 3, 10 and 30 mg/kg) orally for 8 weeks. At the end of the experiment, blood samples were collected and biochemistry analysis was performed. Specimens from both tibia and liver were processed for light microscopic examination. DEXA and μ-CT analyses of the tibia were also performed.

RESULTS

SM treatment significantly ameliorated the decrease in BMD and trabecular bone mass according to DEXA and trabecular bone architecture analysis of trabecular bone structural parameters by μ-CT scanning. In serum biochemical analysis, SM decreased the released TRAP-5b, an osteoclast activation marker and oxidative stress parameters including MDA and NO induced by OVX.

CONCLUSIONS

The preventive effect of SM was presumably due to its anti-oxidative stress partly via modulation of osteoclast maturation and number. In current study, SM appears to be a promising osteoporosis therapeutic natural product.

Spinal cord injury causes more damage to fracture healing of later phase than ovariectomy in young mice

The purpose of this study was to compare the effects of spinal cord injury (SCI) and ovariectomy (OVX) on femoral fracture healing of later phase in young mice. Sixty young female C57 mice were randomized into three groups: SCI, OVX, and age-matched intact control. The femoral fracture was generated at 3 weeks after SCI or OVX. At 1 month after fracture, the femoral fracture area was evaluated through the healing status using radiograph; bone mineral density using dual X-ray absorptometry; callus formation and mineralization and neovascularization in callus using micro-computed tomography; biomechanical analysis using testing machine; and histology analysis by staining with hematoxylin-eosin stain. SCI mice showed lower bone mineral density in the femoral callus as compared with OVX mice. Callus geometric microstructural parameters of the femora in SCI mice were significantly lower than OVX mice. SCI induced significant changes of biomechanical parameters in the femoral fracture healing area. The callus formation and callus neovascularization in SCI mice were significantly lower than in OVX mice. SCI induces more deterioration of fracture healing in the femoral diaphysis than OVX.

Breast tumors induced by N-methyl-N-nitrosourea are damaging to bone strength, structure, and mineralization in the absence of metastasis in rats

Current theory on the influence of breast cancer on bone describes metastasis of tumor cells to bone tissue, followed by induction of osteoclasts and bone degradation. Tumor influences on bone health in pre- or nonmetastatic models are unknown. Female rats (n = 48, 52 days old) were injected with N-methyl-N-nitrosourea (MNU) to induce breast cancer. Animals were euthanized 10 weeks later, and tumors were weighed and classified histologically. Right femurs were extracted for testing of bone mineral density (BMD) by dual X-ray absorptiometry (DXA), bone mechanical strength by three-point bending and femoral neck bending tests, and structure by micro-computed tomography (µCT). Of 48 rats, 22 developed one or more tumors in response to MNU injection by 10 weeks. Presence of any tumor predicted significantly poorer bone health in 17 of 28 measures. In tumored versus nontumored animals, BMD was adversely affected by 3%, force at failure of the femoral midshaft by 4%, force at failure of the femoral neck by 12%, and various trabecular structural parameters by 6% to 27% (all p < .05). Similarly, greater tumor burden, represented by total tumor weight, adversely correlated with bone outcomes: r = -0.51 for BMD, -0.42 and -0.35 for femur midshaft force and work at failure, and between 0.36 and 0.59 (absolute values) for trabecular architecture (all p < .05). Presence of MNU-induced tumors and total tumor burden showed a negative association with bone health of the femur in rats in the absence of metastasis. Further study is required to elucidate mechanisms for this association.

Bone loss and impaired fracture healing in spinal cord injured mice

Spinal cord injury (SCI) results in impaired fracture healing in mice while leading to significant bone loss. Poor fracture healing following SCI is consistent with significant bone loss.

INTRODUCTION

SCI leads to significant bone loss in sublesional limbs, but there is few data concerning the relationship between fracture healing and bone loss following SCI. This study was undertaken to investigate the effect of SCI on fracture healing using a mouse femur fracture model.

METHODS

One hundred twenty male C57BL/6J mice were randomly divided into SCI and control groups (n=60, respectively). A femoral shaft fracture was generated and fixed with intramedullary pins 3 weeks after SCI. Fracture healing was evaluated by micro-computed tomography (micro-CT) for callus formation and mineralization and neovascularization, and bone mineral density (BMD) was measured by DXA at 1, 2, and 4 weeks after fracture. Serum vascular endothelial growth factor (VEGF), osteocalcin, and alkaline phosphatase (ALP) were assessed using ELISA at each time point. Biomechanical testing was performed at 2 and 4 weeks.

RESULTS

BMD in SCI mice was significantly lower compared to control mice at each time point, with callus volume and all vessel parameters reduced as measured by micro-CT. Ultimate stress of the femora was significantly lower in SCI mice than in control mice at 2 and 4 weeks after fracture, whereas Young's modulus between the SCI and control mice turned to be significantly different at 4 weeks. Serum VEGF was lower in SCI mice than in the control group at 2 and 4 weeks, whereas serum osteocalcin and ALP were lower in SCI mice than in control ones at each time point.

CONCLUSION

Significant bone loss and fracture healing impairment was noted in SCI mice. Decreased angiogenesis is consistent with the changes of microarchitecture and biomechanical properties during fracture healing.

The effects of loading and estrogen on rat bone growth

This study evaluated the contributions of locomotive loading and estrogen to the development of diaphysis of rat femur. A randomized 2 × 2 study design was used. Altogether, 70 female Sprague-Dawley rats were used, of which 10 were euthanized at entry. Of the remaining rats, 16 served as controls, and the rest, 44, underwent a unilateral sciatic neurectomy. The effect of estrogen was removed by ovariectomizing one-half of the neurectomized rats. After 27 wk, the animals were euthanized, and the femora were excised. Irrespective of loading or estrogen, the femur length and mineral mass increased by 142 and 687%, respectively. Axial growth was not modulated either by locomotive loading or estrogen, but the loading resulted in direction-specific changes in the cross-sectional geometry. The estrogen-related gains were evident on the endocortical surface, while the loading-related gains occurred on the periosteal surface. The loading and estrogen were significantly associated with increased bone strength (21 and 15%, respectively) in the mediolateral direction, but not in the anteroposterior direction. Axial growth and accrual of bone mineral mass of the rat femur are largely independent of locomotive loading or estrogen, whereas these factors specifically account for the femur function, as either a mechanical lever or a mineral reservoir for reproduction, respectively.

Regional variations of gender-specific and age-related differences in trabecular bone structure of the distal radius and tibia

Regional variation in trabecular structure across axial sections is often obscured by the conventional global analysis, which takes an average value for the entire trabecular compartment. The objective of this study is to characterize spatial variability in trabecular structure within a cross-section at the distal radius and tibia, and gender and age effects using in vivo high-resolution peripheral quantitative computed tomography (HR-pQCT). HR-pQCT images of the distal radius and tibia were acquired from 146 healthy individuals aged 20-78 years. Trabecular bone volume fraction (BV/TV), number (Tb.N), thickness (Tb.Th), separation (Tb.Sp), and heterogeneity (Tb.1/N.SD) were obtained in a total of 11 regions-the entire trabecular compartment (the global means), inner, outer, and eight defined subregions. Regional variations were examined with respect to the global means, and compared between women and men, and between young (20-29 years old) and elderly (65-79 years old) adults. Substantial regional variations in trabecular bone structure at the distal radius and tibia were revealed (e.g. BV/TV varied -40% to +57% and -59% to +100% of the global means, respectively, for elderly women). The inner-lateral (IL) subregion had low BV/TV, Tb.N, and Tb.Th, and low Tb.Sp and Tb.1/N.SD at both sites; the opposite was true in the outer-anterior (OA) subregion at the distal radius and the outer-medial (OM) and -posterior (OP) subregions at the distal tibia. Gender differences were most pronounced in the inner-anterior (IA) subregion compared to the other regions or the global mean differences at both sites. Trabecular structure associated with age and differed between young and elderly adults predominantly in the inner-posterior (IP) subregion at the distal radius and in the IL and IA subregions at the distal tibia; on the other hand, it remained unchanged in the OA subregion at the distal radius and in the OM subregion at the distal tibia for both women and men. This study demonstrated that not only the conventional global analysis can obscure regional differences, but also assuming bone status from that of smaller subregion may introduce a confounding sampling error. Therefore, a combined approach of investigating the entire region, each subregion, and the cortical compartment may offer more complete information.

A longitudinal Raman microspectroscopic study of osteoporosis induced by spinal cord injury

INTRODUCTION

A longitudinal study was established to investigate bone compositional information in spinal cord injury (SCI) rat model.

METHODS

Raman spectroscopy was applied to detect the distal femur and humeri of SCI, sham-operated (SO), and age-matched control (CON) male Sprague-Dawley (SD) rats at first, second, third, and fifth weeks after surgery. One-way ANOVA and Tukey's HSD post hoc multiple comparison tests were used to analyze the longitudinal data of mineral to matrix ratio and carbonate substitution.

RESULTS

Relative mineral decrease was found in SCI group by more than 20% in femur and approximately 12% in humeri compared with CON group. No significant changes in carbonate substitution were observed.

CONCLUSIONS

Severe bone loss in the early stage of SCI was confirmed by a continuous decrease of the mineral to collagen matrix ratio. The decrease in the humeri suggested hormone level variations might participate in the etiology of SCI-induced osteoporosis.

Shortcomings of DXA to assess changes in bone tissue density and microstructure induced by metabolic bone diseases in rat models

The aim of this study is to demonstrate the deficiencies of dual-energy X-ray absorptiometry (DXA), compared with quantitative computed tomography, to reflect and differentiate between changes in bone mineral density and microstructure that contribute to a well-defined finding of altered skeletal state for both osteoporosis and renal osteodystrophy induced by chronic renal insufficiency.

INTRODUCTION

The aim of this study is to demonstrate the deficiencies of dual-energy X-ray absorptiometry (DXA), compared with quantitative CT, to reflect and differentiate between changes in bone mineral density and microstructure that contribute to a well-defined finding of altered skeletal state for both osteoporosis and renal osteodystrophy induced by chronic renal insufficiency.

METHODS

Forty-five female Sprague-Dawley rats were divided into three equal groups: control, ovariectomy, and nephrectomy. Following euthanasia, femurs were excised, divided into diaphyseal and distal metaphyseal sections, and subjected to DXA and micro-CT imaging and mechanical testing.

RESULTS

Ovariectomy does not affect the structural and mechanical properties of cortical bone material, but partial nephrectomy does adversely affect these properties. Both are verified by DXA and micro-CT imaging and mechanical testing. Meanwhile, nephrectomy does not affect trabecular bone microstructure or equivalent density, yet ovariectomy affects the trabecular microstructure. DXA is unable to detect changes in trabecular bone microstructure in relation to changes in their mechanical properties.

DISCUSSION

Dual energy X-ray absorptiometry measures the average bone mineral content in a 2D projected area and cannot differentiate whether the changes occur in the bone microstructure or equivalent bone tissue density. In contrast, micro-CT provides an accurate measurement of the changes in both equivalent bone tissue mineral density and microstructure for cancellous and cortical bone.

Bone degeneration and recovery after early and late bisphosphonate treatment of ovariectomized wistar rats assessed by in vivo micro-computed tomography

Bisphosphonates are antiresorptive drugs commonly used to treat osteoporosis. It is not clear, however, what the influence of the time point of treatment is. Recently developed in vivo micro-computed tomographic (CT) scanners offer the possibility to study such effects on bone microstructure in rats. The aim of this study was to determine the influence of early and late zoledronic acid treatment on bone in ovariectomized rats, using in vivo micro-CT. Twenty-nine female Wistar rats were divided into the following groups: ovariectomy (OVX, n = 5), OVX and zoledronic acid (ZOL) at week 0 (n = 8), OVX and ZOL at week 8 (n = 7), and sham (n = 9). CT scans were made of the proximal tibia at weeks 0, 2, 4, 8, 12, and 16; and bone structural parameters were determined in the metaphysis. Two fluorescent labels were administered to calculate dynamic histomorphometric parameters. At week 16, all groups were significantly different from each other in bone volume fraction (BV/TV), connectivity density, and trabecular number (Tb.N), except for the early ZOL and control groups which were not significantly different for any structural parameter. After ZOL treatment at week 8, BV/TV, structure model index, Tb.N, and trabecular thickness significantly improved in the late ZOL group. The OVX and ZOL groups showed, respectively, higher and lower bone formation rates than the control group. Early ZOL treatment inhibited all bone microstructural changes seen after OVX. Late ZOL treatment significantly improved bone microstructure, although the structure did not recover to original levels. Early ZOL treatment resulted in a significantly better microstructure than late treatment. However, late treatment was still significantly better than no treatment.