A study of trabecular bones in ovariectomized goats with micro-computed tomography and peripheral quantitative computed tomography

In vitro and in vivo degradation behavior of Mg-2Sr-Ca and Mg-2Sr-Zn alloys

Magnesium alloys with integration of degradability and good mechanical performance are desired for orthopedic implants. In this paper, Mg-2Sr-Ca and Mg-2Sr-Zn alloys were prepared and the degradation as well as the bone response were investigated. Compared with the binary Mg-2Sr alloys, the addition of Ca and Zn improved the in vitro and in vivo corrosion resistance. Mg-2Sr-Ca and Mg-2Sr-Zn alloys exhibited more uniform corrosion and maintained the configuration of the implants 4 weeks post-implantation. The in vivo corrosion rates were 0.85 mm/yr for Mg-2Sr-Zn and 1.10 mm/yr for Mg-2Sr-Ca in comparison with 1.37 mm/yr for Mg-2Sr. The in vitro cell tests indicated that Mg-2Sr-Ca and Mg-2Sr-Zn alloys exhibited higher MG63 cell viability than Mg-2Sr alloy. Furthermore, these two alloys can promote the mineralization and new bone formation without inducing any significant adverse effects and this sound osteogenic properties suggest its attractive clinical potential.

Effects of Combined Exposure to Cadmium and High-Fat Diet on Bone Quality in Male Mice

This study investigated the effects of combined exposure to low-dose cadmium and high-fat diet on femoral bone quality in male mice. Eight-week-old male SPF C57BL/6J mice were randomly divided into four groups: normal control group (Con), low-cadmium group (Cd), high-fat diet group (HFD), and high-fat diet plus low-dose cadmium group (HFD + Cd); the second and fourth groups were treated intraperitoneally with CdCl₂ (1.0 mg/kg body weight) twice weekly for 20 weeks. Assays related to bone quality were performed. Body weight of HFD plus Cd mice was significantly lower than HFD mice. Femoral length was not different among groups, but femoral weight was decreased in the HFD plus Cd group compared with other three groups. Level of Cd in bone was significantly increased in HFD plus Cd group. There was no difference in cortical BMD among groups; however, cortical bone quality parameters were decreased in HFD plus Cd group. Cd and HFD each reduced trabecular bone quality and together had further detrimental effects on these bone parameters. Based on biomechanical analysis, femoral bone strength was decreased, being more brittle and less resistant to biomechanical forces in the HFD plus Cd mice. HFD plus Cd mice had lower OPG mRNA expression and higher RANKL mRNA expression than others. HFD or Cd can cause adverse effects on bone and together had further detrimental effects associated with RANKL/OPG signaling.

Preclinical and Translational Studies in Small Ruminants (Sheep and Goat) as Models for Osteoporosis Research

PURPOSE OF THE REVIEW

This review summarizes research on the use of sheep and goats as large animal models of human osteoporosis for preclinical and translational studies.

RECENT FINDINGS

The most frequent osteoporotic sheep model used is the ovariectomized sheep with 12 months post-operatively or more and the combined treatment of ovariectomized sheep associated to calcium/vitamin D-deficient diet and glucocorticoid applications for 6 months, but other methods are also described, like pinealectomy or hypothalamic-pituitary disconnection in ovariectomized sheep. The goat model for osteoporosis research has been used in a very limited number of studies in osteoporosis research relative to sheep. These osteoporotic small ruminant models are applied for biomaterial research, bone augmentation, efficacy of implant fixation, fragility fracture-healing process improvement, or bone-defect repair studies in the osteopenic or osteoporotic bone. Sheep are a recognized large animal model for preclinical and translational studies in osteoporosis research and the goat to a lesser extent. Recently, the pathophysiological mechanism underlying induction of osteoporosis in glucocorticoid-treated ovariectomized aged sheep was clarified, being similar to what occurs in postmenopausal women with glucocorticoid-induced osteoporosis. It was also concluded that the receptor activator of NF-κB ligand was stimulated in the late progressive phase of the osteoporosis induced by steroids in sheep. The knowledge of the pathophysiological mechanisms at the cellular and molecular levels of the induction of osteoporosis in small ruminants, if identical to humans, will allow in the future, the use of these animal models with greater confidence in the preclinical and translational studies for osteoporosis research.

Microstructural properties of trabecular bone autografts: comparison of men and women with and without osteoporosis

The microstructure of autologous bone grafts from men over 50 years old and postmenopausal women undergoing spinal fusion were evaluated using micro-CT. We demonstrated postmenopausal women, especially those with osteoporosis (OP) presented more serious microarchitectural deterioration of bone grafts.

PURPOSE

This study was undertaken to determine microstructural properties of cancellous bone used as autologous bone grafts from osteoporosis patients undergoing lumbar fusion by comparing microstructural indices to controls.

METHODS

Cancellous bone specimens from spinous processes were obtained from 41 postmenopausal women (osteoporosis women, n = 19; controls, n = 22) and 26 men over 50 years old (osteoporosis men, n = 8; controls, n = 18) during lumbar fusion surgery. The microstructural parameters were measured using micro-CT.

RESULTS

Significant difference in bone volume fraction (BV/TV), specific bone surface (BS/BV), trabecular thickness (Tb.Th), and structure model index (SMI) value existed between postmenopausal women with OP and controls. Significant difference in trabecular number (Tb.N) existed between men over 50 years old with OP and controls. Postmenopausal women exhibited lower BV/TV, Tb.Th, and higher SMI value than men over 50 years old. Postmenopausal women with OP exhibited lower BV/TV, Tb.Th, and higher BS/BV than men over 50 years old with OP.

CONCLUSIONS

Post-menopausal women and older men with OP have worse bone quality in autografts than non-osteoporotic men and women. Postmenopausal women with OP presented serious microarchitectural deterioration in older population.

β‑Ecdysterone promotes autophagy and inhibits apoptosis in osteoporotic rats

Osteoporosis is an aging process of skeletal tissues with characteristics of reductions in bone mass and microarchitectural deterioration of bone tissue. The present study aimed to investigate the effects of glucocorticoid-induced osteoporosis on osteoblasts and to examine the roles of β-ecdysterone (β-Ecd) involved. In the present study, an in vivo model of osteoporosis was established through the subcutaneous implantation of prednisolone (PRED) into Sprague-Dawley rats, with or without a subcutaneous injection of β-Ecd (5 or 10 mg/kg body weight). Expression of Beclin-1 and microtubule-associated protein 1A/1B-light chain 3I/II and apoptosis in lumbar vertebrae tissues was measured by immunofluorescence and TUNEL assays, respectively. Serum concentration of calcium and phosphorus, and the activity of tartrate-resistant acid phosphatase (TRAP) and alkaline phosphatase (ALP) were measured by biochemical assay. Reverse transcription-quantitative polymerase chain reaction and western blotting was used for detect the expression of related genes and proteins. PRED treatment inhibited bone formation by decreasing bone mineral density, and suppressing the expression of Runt-related transcription factor 2 and bone morphogenetic protein 2, while enhancing the activity of alkaline phosphatase, upregulating the expression of receptor activator of nuclear factor-κB ligand, and increasing the serum content of calcium, phosphorus and tartrate-resistant acid phosphatase in rats. Additionally, PRED was revealed to inhibit autophagy through the downregulation of Beclin-1, autophagy protein 5 and microtubule-associated protein 1A/1B-light chain 3I/II expression, whereas it induced the apoptosis, through the activation of caspase-3 and the suppression of apoptosis regulator BCL2 expression. Notably, the PRED-induced alterations in bone formation, autophagy and apoptosis were revealed to be attenuated by β-Ecd administration. In conclusion, the findings of the present study suggested that β-Ecd may be a promising candidate for the development of therapeutic strategies for the treatment of osteoporosis, through the induction of autophagy and the inhibition of apoptosis in vivo.

Mechanical stimulation enhanced estrogen receptor expression and callus formation in diaphyseal long bone fracture healing in ovariectomy-induced osteoporotic rats

Estrogen receptor (ER) in ovariectomy-induced osteoporotic fracture was reported to exhibit delayed expression. Mechanical stimulation enhanced ER-α expression in osteoporotic fracture callus at the tissue level. ER was also found to be required for the effectiveness of vibrational mechanical stimulation treatment in osteoporotic fracture healing.

INTRODUCTION

Estrogen receptor(ER) is involved in mechanical signal transduction in bone metabolism. Its expression was reported to be delayed in osteoporotic fracture healing. The purpose of this study was to investigate the roles played by ER during osteoporotic fracture healing enhanced with mechanical stimulation.

METHODS

Ovariectomy-induced osteoporotic SD rats that received closed femoral fractures were divided into five groups, (i) SHAM, (ii) SHAM-VT, (iii) OVX, (iv) OVX-VT, and (v) OVX-VT-ICI, where VT stands for whole-body vibration treatment and ICI for ER antagonization by ICI 182,780. Callus formation and gene expression were assessed at 2, 4, and 8 weeks postfracture. In vitro osteoblastic differentiation, mineralization, and ER-α expression were assessed.

RESULTS

The delayed ER expression was found to be enhanced by vibration treatment. Callus formation enhancement was shown by callus morphometry and micro-CT analysis. Enhancement effects by vibration were partially abolished when ER was modulated by ICI 182,780, in terms of callus formation capacity at 2-4 weeks and ER gene and protein expression at all time points. In vitro, ER expression in osteoblasts was not enhanced by VT treatment, but osteoblastic differentiation and mineralization were enhanced under estrogen-deprived condition. When osteoblastic cells were modulated by ICI 182,780, enhancement effects of VT were eliminated.

CONCLUSIONS

Vibration was able to enhance ER expression in ovariectomy-induced osteoporotic fracture healing. ER was essential in mechanical signal transduction and enhancement in callus formation effects during osteoporotic fracture healing enhanced by vibration. The enhancement of ER-α expression by mechanical stimulation was not likely to be related to the increased expression in osteoblastic cells but rather to the systemic enhancement in recruitment of ER-expressing progenitor cells through increased blood flow and neo-angiogenesis. This finding might explain the observed difference in mechanical sensitivity of osteoporotic fracture to mechanical stimulation.

Bone formation and degradation behavior of nanocrystalline hydroxyapatite with or without collagen-type 1 in osteoporotic bone defects - an experimental study in osteoporotic goats

The intention of the current work is to assess new bone formation and degradation behavior of nanocrystalline hydroxyapatite with (HA/col-1) or without collagen-type I (HA) in osteoporotic metaphyseal bone defects in goats. After ovariectomy and special low-calcium diet for three months, 3 drill hole defects in the vertebrae of L3, L4, L5, 4 drill hole defects in the right and left iliac crest and 1 drill hole defect at the distal femur were created in three Chinese mountain goats with a total of 24 defects. The defects were either filled with one of the biomaterials or left empty (empty defect control group). After 42 days, the animals were euthanized and the samples were assessed for new bone formation using high-resolution peripheral quantitative computed tomography (HR-pQCT) and histomorphometry with 2 regions of interest. Detail histology, enzymehistochemistry and immunohistochemistry as well as connexin-43 in situ hybridization and transmission electron microscopy were carried out for evaluation of degradation behavior of the materials and cellular responses of the surrounding tissue in respect to the implants. HR-pQCT showed the highest BV/TV ratio (p = 0.008) and smallest trabecular spacing (p = 0.005) for HA compared to the other groups in the region of interest at the interface with 1mm distance to the initially created defect. The HA/col-1 yielded the highest connectivity density (Conn.D) (p = 0.034) and the highest number of trabeculae (Tb.N) (p = 0.002) compared to the HA and the control group. Histomorphometric analysis for the core region of the initially created defect revealed a statistically higher new bone formation in the HA (p = 0.001) and HA/col-1 group (p = 0.001) compared to the empty defect group including all defect sites. This result was confirmed for site specific analysis with significant higher new bone formation for the HA group for vertebral defects compared to the empty defect group (p = 0.029). For the interface region, no statistically significant differences were found between the three groups (p = 0.08). Histology revealed a good biocompatibility without inflammatory reaction for the HA- and HA/col-1 implants with a higher fragmentation of the HA-implant compared to the HA/col-1 biomaterial and formation of new bone in the region between the biomaterial fragments by osteoblasts. Fragmentation was shown by transmission electron microscopy to be caused by multinuclear osteoclast-like cells with degradation of the implant via intracellular incorporation of degraded implant material particles. In conclusion, both nanoparticulate HA with and without collagen type-1 showed better new bone formation compared to untreated drill hole defects in metaphyseal regions of this osteoporotic Chinese mountain goat model with good biocompatibility.

Influence of the lateral pterygoid muscle on traumatic temporomandibular joint bony ankylosis

BACKGROUND

The pathogenesis of traumatic TMJ ankylosis remains unclear. This study aimed to verify the role of the lateral pterygoid muscle in the pathogenesis of traumatic temporomandibular joint (TMJ) bony ankylosis.

METHODS

Eight 6-month-old male sheep were used in this study. Bilateral TMJ osteotomies were performed to induce sagittal fractures of the mandibular condyle. The lateral one-fourth segment of the disc was removed to establish a model of TMJ bony ankylosis. Subsequently, the function of the left and right lateral pterygoid muscles was blocked (experimental group) or maintained (control group), respectively. At 12 weeks postoperatively, animals were sacrificed and TMJ complex samples were evaluated by gross observation, spiral computed tomography (CT), micro-CT, and histological examinations.

RESULTS

Gross observation revealed bony ankylosis in the control TMJs and fibrous adhesions in the experimental TMJs. Spiral CT and micro-CT demonstrated that, compared to the experimental group, the control group showed calcified callus formation in the joint space and roughened articular surfaces after new bone formation, which protruded into the joint space. Maximum mediolateral and anteroposterior condylar diameters were significantly larger in the control group than in the experimental group. Micro-CT also showed that the primary growth orientation of new trabeculae was consistent with the direction of lateral pterygoid traction in the control group, but not in the experimental group. Histological examination showed fibro-osseous ankylosis in the control group, but not in the experimental group.

CONCLUSIONS

The lateral pterygoid simulates the effects of distraction osteogenesis, which is an important factor in the pathogenesis of TMJ bony ankylosis during the healing of sagittal condylar fractures.

Positive skeletal effect of two ingredients of Psoralea corylifolia L. on estrogen deficiency-induced osteoporosis and the possible mechanisms of action

Estrogen replacement therapy (ERT) is utilized as a major regime for treatment of postmenopausal osteoporosis at present. However, long-term supplement of estrogen may cause uterine hyperplasia and hypertension leading to a high risk of endometrial cancer and breast cancer. Psoralea corylifolia L. has long been used as tonic and food additives in many countries. Previous studies had found two ingredients in P. corylifolia L.: bavachin and bakuchiol exhibited osteoblastic activity. The present study was designed to investigate the protective effect of bakuchiol and bavachin on ovariectomy-induced bone loss and explore the possible mechanism. In vivo, bakuchiol and bavachin could prevented estrogen deficiency-induced bone loss in ovariectomized rats without uterotrophic activity. In vitro studies suggested that bakuchiol and bavachin induced primary human osteoblast differentiation by up-regulating the Wnt signalling pathway. This study suggests that such a bone-protective role makes them a promising and safe estrogen supplement for the ERT.

The Effects of Elk Velvet Antler Dietary Supplementation on Physical Growth and Bone Development in Growing Rats

Elk velvet antler (EVA) has been used in traditional Oriental medicine for centuries to promote general health; however, little evidence for its effect on bone development is available. We investigated the effects of lifelong exposure of Wistar rats to a diet containing 10% EVA on physical growth and bone development. Measurements included weekly body weights, blood chemistry and kidney and testis/ovary indices (sacrificed at 5, 9, or 16 weeks of age), and bone traits of the femur bones by peripheral quantitative computed tomography (pQCT). Mean body weights were higher in the EVA group at 4–8 weeks in males and at 5 weeks of age in females. The kidney indices were greater in EVA dietary supplemented male rats at 5 and 16 weeks of age, in females at 16 weeks of age, and testis/ovary indices at 5 weeks of age. The femoral length was increased in both males and females at 5 weeks, and several pQCT-measured parameters had increased in EVA males and females. The activity of alkaline phosphatase (ALP) increased in EVA group while the content of calcium and phosphorus did not differ among groups. Our results seem to support a role for dietary supplementation of EVA on growth and bone development in this model.

Development of biodegradable Zn-1X binary alloys with nutrient alloying elements Mg, Ca and Sr

Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals.

Bone quality: the determinants of bone strength and fragility

Bone fragility is a major health concern, as the increased risk of bone fractures has devastating outcomes in terms of mortality, decreased autonomy, and healthcare costs. Efforts made to address this problem have considerably increased our knowledge about the mechanisms that regulate bone formation and resorption. In particular, we now have a much better understanding of the cellular events that are triggered when bones are mechanically stimulated and how these events can lead to improvements in bone mass. Despite these findings at the molecular level, most exercise intervention studies reveal either no effects or only minor benefits of exercise programs in improving bone mineral density (BMD) in osteoporotic patients. Nevertheless, and despite that BMD is the gold standard for diagnosing osteoporosis, this measure is only able to provide insights regarding the quantity of bone tissue. In this article, we review the complex structure of bone tissue and highlight the concept that its mechanical strength stems from the interaction of several different features. We revisited the available data showing that bone mineralization degree, hydroxyapatite crystal size and heterogeneity, collagen properties, osteocyte density, trabecular and cortical microarchitecture, as well as whole bone geometry, are determinants of bone strength and that each one of these properties may independently contribute to the increased or decreased risk of fracture, even without meaningful changes in aBMD. Based on these findings, we emphasize that while osteoporosis (almost) always causes bone fragility, bone fragility is not always caused just by osteoporosis, as other important variables also play a major role in this etiology. Furthermore, the results of several studies showing compelling data that physical exercise has the potential to improve bone quality and to decrease fracture risk by influencing each one of these determinants are also reviewed. These findings have meaningful clinical repercussions as they emphasize the fact that, even without leading to improvements in BMD, exercise interventions in patients with osteoporosis may be beneficial by improving other determinants of bone strength.

Coadministrating luteolin minimizes the side effects of the aromatase inhibitor letrozole

Aromatase inhibitors (AIs) have been used as adjuvant therapeutic agents for breast cancer. Their adverse side effect on blood lipid is well documented. Some natural compounds have been shown to be potential AIs. In the present study, we compared the efficacy of the flavonoid luteolin to the clinically approved AI letrozole (Femara; Novartis Pharmaceuticals, East Hanover, NJ) in a cell and a mouse model. In the in vitro experimental results for aromatase inhibition, the Ki values of luteolin and letrozole were estimated to be 2.44 µM and 0.41 nM, respectively. Both letrozole and luteolin appeared to be competitive inhibitors. Subsequently, an animal model was used for the comparison. Aromatase-expressing MCF-7 cells were transplanted into ovariectomized athymic mice. Luteolin was given by mouth at 5, 20, and 50 mg/kg, whereas letrozole was administered by intravenous injection. Similar to letrozole, luteolin administration reduced plasma estrogen concentrations and suppressed the xenograft proliferation. The regulation of cell cycle and apoptotic proteins-such as a decrease in the expression of Bcl-xL, cyclin-A/D1/E, CDK2/4, and increase in that of Bax-was about the same in both treatments. The most significant disparity was on blood lipids. In contrast to letrozole, luteolin increased fasting plasma high-density lipoprotein concentrations and produced a desirable blood lipid profile. These results suggested that the flavonoid could be a coadjuvant therapeutic agent without impairing the action of AIs.

In vitro and in vivo studies on biodegradable CaMgZnSrYb high-entropy bulk metallic glass

In order to enhance the corrosion resistance of the Ca65Mg15Zn20 bulk metallic glass, which has too fast a degradation rate for biomedical applications, we fabricated the Ca20Mg20Zn20Sr20Yb20 high-entropy bulk metallic glass because of the unique properties of high-entropy alloys. Our results showed that the mechanical properties and corrosion behavior were enhanced. The in vitro tests showed that the Ca20Mg20Zn20Sr20Yb20 high-entropy bulk metallic glass could stimulate the proliferation and differentiation of cultured osteoblasts. The in vivo animal tests showed that the Ca20Mg20Zn20Sr20Yb20 high-entropy bulk metallic glass did not show any obvious degradation after 4 weeks of implantation, and they can promote osteogenesis and new bone formation after 2 weeks of implantation. The improved mechanical properties and corrosion behavior can be attributed to the different chemical composition as well as the formation of a unique high-entropy atomic structure with a maximum degree of disorder.

The beneficial effect of icaritin on osteoporotic bone is dependent on the treatment initiation timing in adult ovariectomized rats

BACKGROUND

Epimedium-derived flavonoids (EFs) have a potential to treat established osteoporosis in postmenopausal women. However, one of the main disadvantages of the compound is the high volume and dosage during long-term administration period. Meanwhile, the beneficial effect of EFs on osteoporotic bone depends greatly on the intervention timing. Whether icaritin (ICT), an active molecular compound from EFs, can exert beneficial effect on osteoporotic bone and whether the beneficial effect is also dependent on the intervention timing remain unknown.

OBJECTIVE

The objective of this study was to evaluate the effect of the early and late ICT treatment on bone turnover markers, trabecular architecture, bone remodeling, biomechanics, colony formation of bone marrow stromal cells and osteoblast, adipocyte and osteoclast-related gene expression in adult ovariectomized rats.

METHODS

Eighty 9-month-old female rats (n=8/group) were sham-operated (Sham) or ovariectomized (OVX). The OVX rats were subjected to ICT treatment initiation at 1 month (early treatment) and 3 months (late treatment) post-operation, respectively. The vehicle-treated Sham and OVX rats starting at month 1 and month 3 post-operation served as the corresponding controls (Sham and OVX controls) for early and late ICT treatment, respectively. Those Sham and OVX rats sacrificed immediately before early and late ICT treatment served as the pretreatment baseline controls. Both ICT and vehicle treatments lasted for 2 months. The bone turnover markers, trabecular architecture, bone remodeling and bone biomechanical properties were analyzed with biochemistry, microCT, histomorphometry and mechanical testing, respectively. The population of bone marrow stromal cells (BMSCs) and osteoblasts were evaluated with colony formation assays, respectively. The expression levels of osteoblast, adipocyte and osteoclast-related genes in bone marrow were assessed by real-time polymerase chain reaction (PCR), respectively.

RESULTS

At the tissue level, early ICT treatment remarkably restored the trabecular bone mass, trabecular architecture and bone biomechanical properties towards pretreatment Sham levels, and significantly increased bone formation from pretreatment OVX level and markedly inhibited bone resorption towards pretreatment Sham level, whereas late ICT treatment failed to have any effect. At the cellular and molecular level, early ICT treatment significantly increased the number of osteoblastic colonies and the level of osteoblast-related gene expression compared to pretreatment OVX levels and remarkably decreased adipocyte and osteoclast-related gene expression towards pretreatment Sham levels. Late ICT treatment failed to have beneficial effect on any of these parameters.

CONCLUSION

ICT can exert anabolic and anti-resorptive effect on osteoporotic bone. The beneficial effect of ICT treatment is dependent on the intervention timing in established osteoporosis induced by estrogen depletion.

Influence of tool geometry on drilling performance of cortical and trabecular bone

Minimally invasive surgery poses high demands on tool design. The goal was to measure the influence of drill bit geometry on maximum thrust forces required for drilling, and compare this relative to the known influence of feed rate and bone composition. Blind holes were drilled perpendicular to the iliac crest up to 10 mm depth in cadaveric pelvic bones of 20 pigs (adolescent) and 11 goats (full grown) with eight substantially different drill bits of ∅ 3-3.2 mm. Subsequently, boreholes were drilled perpendicular to the ilium with the same drill bits at three different feed rates (0.58 mm/s, 0.83 mm/s, 1.08 mm/s). The mean maximum thrust force ranges from 10 to 110 N for cortical bone, and from 3 to 65 N for trabecular bone. The results show that both drill bit geometry and feed rate have a significant influence on the maximum thrust forces, with a dominant influence of drill bit geometry in terms of shape of the flutes, sharpness of cutting edges and value of point angle. The differences in thrust forces between cortical and trabecular bone are substantial for all measured conditions. The measured values can be used for drill design.

Comparative study of osteogenic potential of a composite scaffold incorporating either endogenous bone morphogenetic protein-2 or exogenous phytomolecule icaritin: an in vitro efficacy study

A local delivery system with sustained and efficient release of therapeutic agents from an appropriate carrier is desirable for orthopedic applications. Novel composite scaffolds made of poly (lactic-co-glycolic acid) with tricalcium phosphate (PLGA/TCP) were fabricated by an advanced low-temperature rapid prototyping technique, which incorporated either endogenous bone morphogenetic protein-2 (BMP-2) (PLGA/TCP/BMP-2) or phytomolecule icaritin (ICT) (PLGA/TCP/ICT) at low, middle and high doses. PLGA/TCP served as control. In vitro degradation, osteogenesis and release tests showed statistical differences among PLGA/TCP/ICT, PLGA/TCP and PLGA/TCP/BMP-2 groups, where PLGA/TCP/ICT had the desired slow release of bioactive icaritin in a dose-dependent manner, whereas there was almost no BMP-2 release from the PLGA/TCP/BMP-2 scaffolds. PLGA/TCP/ICT significantly increased more ALP activity, upregulated mRNA expression of osteogenic genes and enhanced calcium deposition and mineralization in rabbit bone marrow stem cells cultured on scaffolds compared with the other two groups. These results indicate the desired degradation rate, osteogenic capability and release property in PLGA/TCP/ICT composite scaffold, as icaritin preserved its bioactivity and structure after incorporation, while PLGA/TCP/BMP-2 did not show an initially expected osteogenic potential, owing to loss of the original bioactivity of BMP-2 during its incorporation and fabrication procedure. The results suggest that PLGA/TCP composite scaffolds incorporating osteogenic ICT might be a promising approach for bone tissue bioengineering and regeneration.

Trabecular bone micro-architecture and bone mineral density in adolescent idiopathic and congenital scoliosis

OBJECTIVE

To investigate the microstructure of trabecular bone in adolescent idiopathic scoliosis (AIS) and age-matched congenital scoliosis (CS), and to evaluate the bone mineral status of CS patients compared with normal controls and AIS patients.

METHODS

This study included 15 AIS and 16 CS female patients and 35 healthy female adolescents. Corrective surgery was indicated for the AIS and CS patients, from whom iliac crest biopsies were collected during autograft harvesting, and scanned by micro-computer tomography. Bone mineral status was assessed at the lumbar and hip areas in every patient by dual energy X-ray absorptiometry (DEXA).

RESULTS

Significantly lower lumbar and femoral neck bone mineral density (BMD) was found in AIS patient compared with normal controls. All BMD and bone mineral content (BMC) parameters were significantly lower in CS patients compared with age-matched normal controls. Under DEXA assessment significant associations between bone volume/tissue volume (BV/TV) and BMD values were observed. In the 3D model, BV/TV was significantly higher in AIS (19.9% ± 3.4%) than in CS (13.3% ± 3.0%, P < 0.05). Significant differences between AIS and CS were also found in trabecular thickness (Tb.Th) and bone surface/bone volume (BS/BV) (155.5 ± 54.9 µm vs. 108.1 ± 17.4 µm and 16.4% ± 3.3% vs. 22.0% ± 3.4% respectively, P < 0.05 in both).

CONCLUSION

Lower bone mineral status and weak trabecular bone structure observed in AIS and CS justify further investigation of the bone mineral status in scoliosis of various etiologies.

Biodegradable CaMgZn bulk metallic glass for potential skeletal application

A low density and high strength alloy, Ca65Mg15Zn20 bulk metallic glass (CaMgZn BMG), was evaluated by both in vitro tests on ion release and cytotoxicity and in vivo implantation, aimed at exploring the feasibility of this new biodegradable metallic material for potential skeletal applications. MTT assay results showed that the experimental CaMgZn BMG extracts had no detectable cytotoxic effects on L929, VSMC and ECV304 cells over a wide range of concentrations (0-50%), whereas for MG63 cells concentrations in the range ~5-20% promoted cell viability. Meanwhile, alkaline phosphatase (ALP) activity results showed that CaMgZn BMG extracts increased alkaline phosphatase (ALP) production by MG63 cells. However, Annexin V-fluorescein isothiocyanate and propidium iodide staining indicated that higher concentrations (50%) might induce cell apoptosis. The fluorescence observation of F-actin and nuclei in MG63 cells showed that cells incubated with lower concentrations (0-50%) displayed no significant change in morphology compared with a negative control. Tumor necrosis factor-α expression by Raw264.7 cells in the presence of CaMgZn BMG extract was significantly lower than that of the positive and negative controls. Animal tests proved that there was no obvious inflammation reaction at the implantation site and CaMgZn BMG implants did not result in animal death. The cortical thickness around the CaMgZn BMG implant increased gradually from 1 to 4 weeks, as measured by in vivo micro-computer tomography.

Micro-CT and mechanical evaluation of subchondral trabecular bone structure between postmenopausal women with osteoarthritis and osteoporosis

SUMMARY

An inverse relationship between osteoarthritis and osteoporosis has been debated over years. The microstructure of the femoral heads from postmenopausal osteoarthritic and osteoporotic women was evaluated with micro-CT. Significant differences were observed in microstructural parameters between them. Different microstructure might relate to the opposite bone defects in osteoarthritis and osteoporosis.

INTRODUCTION

This study was undertaken to verify the inverse relationship between osteoarthritis (OA) and osteoporosis (OP) by comparing the structural and mechanical indices.

METHODS

Femoral head specimens were obtained from 17 postmenopausal women (OA, n = 8; OP, n = 9) during hip surgery. The microstructural parameters were measured with micro-CT. Mechanical test was performed after bone cube scanning.

RESULTS

Significant difference in bone volume fraction (BV/TV) and trabecular thickness was noted between OA and OP groups. Structure model index decreased in OA, and increased in OP. The higher apparent density (AD) and lower material density (MD) were also shown in OA. Different from OP, positive correlation were noted between connectivity density and mechanical indices in OA. In OA group, BV/TV was associated with Young's modulus and AD, while trabecular number was the only parameter that correlated with MD. However, in OP group, only BV/TV correlated with yield strength, AD, and MD.

CONCLUSIONS

We observed the difference in microstructure between postmenopausal women with OA and OP, which might relate to the opposite bone defects in OA and OP. BV/TV might play an important role in mechanical properties of the subchondral bone in either OA or OP.

Calcium phosphate cement with BMP-2-loaded gelatin microspheres enhances bone healing in osteoporosis: a pilot study

BACKGROUND

The capacity for bone healing reportedly is limited in osteoporosis with a less than ideal environment for healing of bone grafts. We therefore developed a composite bone substitute with rhBMP-2 loaded gelatin microsphere (GM) and calcium phosphate cement (CPC) to use in osteoporosis.

QUESTIONS/PURPOSES

We asked whether (1) controlled release of rhBMP-2 could be improved in this composite bone substitute and (2) increasing factors released from the bone substitute could accelerate osteoporotic bone healing.

METHODS

We soaked rhBMP-2/GM/CPC and rhBMP-2/CPC composites in simulated body fluid for 28 days and then determined the amount of rhBMP-2 released. Both composites were implanted in bone defects of osteoporotic goats and left in place for 45 and 140 days; the specimens then were evaluated mechanically (pushout test) and morphologically (CT scanning, histology).

RESULTS

The in vitro study showed the new composite released more rhBMP-2 compared with rhBMP-2/CPC. CT showed the defects healed more quickly with new grafts. The bone mineralization rate was greater in rhBMP-2/GM/CPC than in rhBMP-2/CPC after 45 days of implantation and the pushout test was stronger after 45 and 140 days of implantation.

CONCLUSIONS

The new graft composite released more loaded factors and appeared to repair osteoporotic bone defects.

CLINICAL RELEVANCE

These preliminary data suggest the new composite can be used as a bone substitute to accelerate healing of fractures and bone defects in osteoporosis.

The design and use of animal models for translational research in bone tissue engineering and regenerative medicine

This review provides an overview of animal models for the evaluation, comparison, and systematic optimization of tissue engineering and regenerative medicine strategies related to bone tissue. This review includes an overview of major factors that influence the rational design and selection of an animal model. A comparison is provided of the 10 mammalian species that are most commonly used in bone research, and existing guidelines and standards are discussed. This review also identifies gaps in the availability of animal models: (1) the need for assessment of the predictive value of preclinical models for relative clinical efficacy, (2) the need for models that more effectively mimic the wound healing environment and mass transport conditions in the most challenging clinical settings (e.g., bone repair involving large bone and soft tissue defects and sites of prior surgery), and (3) the need for models that allow more effective measurement and detection of cell trafficking events and ultimate cell fate during the processes of bone modeling, remodeling, and regeneration. The ongoing need for both continued innovation and refinement in animal model systems, and the need and value of more effective standardization are reinforced.

Low intensity pulsed ultrasound increases the mechanical properties of the healing tissues at bone-tendon junction

The re-establishment of bone-tendon junction (BTJ) tissues is involved in many trauma and reconstructive surgeries. A direct BTJ repair requires a long period of immobilization which may be associated with a postoperative weak knee. In this study, we investigated if low-intensity pulsed ultrasound treatment increases the material properties of healing tissues at bone-tendon junction (BTJ) after partial patellectomy using rabbit models. Standard partial patellectomy was conducted on one knee of twenty four rabbits which were randomly divided into an ultrasound group and a control group. The bony changes of BTJ complexes around the BTJ healing interface were measured by anteroposterior x-ray radiographs; then the volumetric bone-mineral density (BMD) of the new bone was assessed using a peripheral computed tomography scanner (pQCT). The stiffness of patellar cartilage, fibrocartilage at the healing interface and the tendon were measured in situ using a novel noncontact ultrasound water jet indentation system. Not only significantly more newly formed bone at the BTJ healing interface but also increased stiffness of the junction tissues were found in the ultrasound group compared with the controls at week 18. In addition, the ultrasound group also showed significantly 44% higher BMD at week 6 than controls.

Influence of bone adaptation on tendon-to-bone healing in bone tunnel after anterior cruciate ligament reconstruction in a rabbit model

Anterior cruciate ligament (ACL) reconstruction with placement of grafted tendon in bone tunnel is a common surgical procedure. Bone tunnel creation may result in stress shielding of postero-lateral regions of tibial tunnel. The present study was designed to characterize the changes of peri-graft bone and compare with tendon-to-bone (T-B) healing in spatial and temporal manners after ACL reconstruction in rabbit. Surgical reconstruction using digital extensor tendon in bone tunnel was performed on 48 rabbits. Twelve rabbits were sacrificed at 0, 2, 6, and 12 weeks postoperatively for radiological and histological examinations. Bone mass and microarchitecture at the anterior, posterior, medial, and lateral regions of tunnel wall at distal femur and proximal tibia were evaluated. Using peripheral quantitative computed tomography, a 26, 22, and 42% decrease in bone mineral density (BMD) relative to baseline was present in the medial region of the femoral tunnel and the posterior and lateral regions of the tibial tunnel, respectively, at week 12 postoperatively (p < 0.05). It was accompanied by a decrease in trabecular number and increase in trabecular spacing, the shift of platelike to rodlike trabeculae, and loss of anisotropy under micro-computed tomography evaluation. This finding was echoed by histology showing increased osteoclastic activities and poor T-B healing in these regions. In conclusion, the postoperative bone loss and associated poor T-B healing was region-dependent, which may result from adaptive changes after tunnel creation.

Epimedium-derived flavonoids promote osteoblastogenesis and suppress adipogenesis in bone marrow stromal cells while exerting an anabolic effect on osteoporotic bone

BACKGROUND

Epimedium-derived flavonoids (EFs) have been reported to prevent bone loss in ovariectomized (OVX) rats and late postmenopausal women but the underlying mechanism of the anabolic effect is unknown.

OBJECTIVE

This study aimed to investigate the effect of EFs on osteoporotic bone using histomorphometry and on osteoblastogenesis/adipogenesis of bone marrow stromal cells (BMSCs).

METHODS

11-month-old female Wistar rats were divided into Sham, OVX, Sham+soluble vehicle (Sham+SV), OVX+SV and OVX+EFs (10 mg/kg/day) groups. 3 months after surgery, rats from the first two groups were euthanized to verify the establishment of OVX-induced osteoporosis. Other groups were orally treated with either daily SV or EFs for 4 months. At sacrifice, serum was analyzed for the levels of osteocalcin and TRACP 5b, BMD in the proximal femur was measured by pQCT. Static and dynamic bone histomorphometry was performed in proximal tibiae with microCT and undecalcified sections, respectively. The effect of EF treatment on differentiation of rat BMSCs was assessed by colony formation assays and gene expression analysis, respectively. Gene expression, ALP activity and adipocyte numbers were determined in differentiating human BMSCs after exposure to conditioned serum from SV- or EFs-treated OVX rats.

RESULTS

The serum level of osteocalcin was higher and TRACP 5b was lower in EFs versus SV-treated OVX rats. BMD, BV/TV, Tb.N and Conn.D in EFs-treated OVX rats were significantly greater than those of SV-treated OVX rats. Bone histomorphometric parameters OS/BS, MAR, and BFR/BS were significantly higher in EFs versus SV-treated OVX rats. EFs significantly increased osteogenesis and decreased adipogenesis of BMSCs, as evidenced by CFU-ALP and CFU-Adipo assays, respectively. The mRNA level of Runx2 and bone sailoprotein was significantly higher while PPARgamma2 was significantly lower in BMSCs from EFs-treated versus SV-treated OVX rats. ALP activity and Runx2 mRNA was significantly higher while adipocyte number and PPARgamma2 mRNA was significantly lower in human BMSCs after exposure to conditioned serum from EFs versus SV-treated OVX rats.

CONCLUSION

EFs exerted anabolic effect on osteoporotic bone by concomitantly promoting osteogenic and suppressing adipogenic differentiation of BMSCs.

Peri-graft bone mass and connectivity as predictors for the strength of tendon-to-bone attachment after anterior cruciate ligament reconstruction

The present study was designed to compare peri-graft bone mass and microarchitecture with tendon-to-bone (T-B) attachment strength after anterior cruciate ligament (ACL) reconstruction in a rabbit model. Surgical reconstruction using digital extensor tendon in bone tunnel was performed on 58 rabbits. Forty-two of the 58 rabbits were sacrificed at week 0, 2, 6 and 12 after operation respectively. The femur-graft-tibia complexes were harvested for pQCT and micro-CT examination to characterize the spatiotemporal changes of peri-graft bone in T-B healing in conjunction with histological examination. The remaining 16 rabbits were euthanized at week 6 and 12 postoperatively (i.e. 8 rabbits for each time point) for pull-out test after micro-CT examination to investigate the relationship between the T-B attachment strength and peri-graft bone mass/microarchitecture. Peri-graft BMD, BV/TV and connectivity was significantly lower at week 6 than those at time zero although there were no significant changes detected in the first 2 postoperative weeks. In addition, peri-graft bone mass and connectivity was significantly lower on the tibial side than those on the femoral side; and osteoclasts accumulated on the surface of peri-graft bone. Grafted tendon was prone to be pulled out from the tibial tunnel with bone attachment; the weakest point of the complexes shifted from the healing interface at time zero to peri-graft bone at week 6 after operation. With reverse of peri-graft bone at week 12 postoperatively, the weakest point shifted to the intra-osseous tendinous portion. The stiffness of T-B attachment correlated with peri-graft BV/TV (r2 = 0.68, p = 0.001) and connectivity (r2 = 0.47, p = 0.013) at week 6 after operation. T-B healing was a highly dynamic process of emergence and maintenance of peri-graft bone. T-B attachment strength was in relation to peri-graft bone mass and connectivity after ACL reconstruction. The measurement of peri-graft bone should be useful to monitor the quality of T-B healing and guide the postoperative rehabilitation.

The use of brushite calcium phosphate cement for enhancement of bone-tendon integration in an anterior cruciate ligament reconstruction rabbit model

This study was designed to investigate the osteoconductivity and bioresorption of brushite calcium phosphate cement (CPC) in bone-tendon interface healing after anterior cruciate ligament (ACL) reconstruction. Surgical reconstruction using grafted tendon in bone tunnel was performed bilaterally in 28 skeletal mature rabbits. Brushite CPC was implanted between grafted tendon and bone tunnel of one limb with the contralateral one as the control. A batch of 14 rabbits was sacrificed at 6 and 12 weeks, respectively, after surgery. At each time point, six rabbits were used for micro-CT and subsequent histological examinations, whereas the remaining eight rabbits were used for pull-out testing. The components of brushite CPC-dicalcium phosphate dihydrate matrix degraded rapidly with beta-tricalcium phosphate granules left for guiding new bone formation. Brushite CPC augmented the peri-tendon bone volume and promoted bone growth into the healing interface. The ultimate strength and stiffness of the graft-tunnel complexes on experimental side was higher than that of the control by 117% and 102%, respectively, at 6 weeks postoperatively (p < 0.05 for both). The use of brushite CPC caused a paradigm shift in failure mode from intra-tunnel to intra-articular portion at 12 weeks postoperatively (p = 0.013). Brushite CPC significantly enhanced the bone-tendon integration after ACL reconstruction, which provided a scientific basis for clinical application.

Shockwave exerts osteogenic effect on osteoporotic bone in an ovariectomized goat model

Our recent in vitro study showed that extracorporeal shock wave (ESW) stimulated calcium deposition in human periosteal cells. In this study, we hypothesized that the use of ESW could induce new bone formation in osteoporotic bone. Using our established osteoporotic goat model, the calcaneus, distal radius and femoral condyle of the left limb were treated with ESW once per month; the contralateral side served as the control. Bone mineral density (BMD), microarchitecture and dynamic histomorphometric index were evaluated after 9 months. Trabecular BMD of the calcaneus increased significantly by 2.90%. This finding was substantiated by micro-computed tomography findings showing that trabecular bone volume fraction and trabecular thickness of the treated calcaneus were enhanced compared with the contralateral control. However, significant difference could not be detected in the other two weight-bearing skeletal sites. Mineral apposition rates of all ESW-treated regions were also consistently higher than those of the control. These findings suggest that ESW treatment could enhance local BMD by inducing new bone formation, yet the effect was more apparent in non-weight-bearing sites.

Longitudinal as well as age-matched assessments of bone changes in the mature ovariectomized rat model

In the past, bone loss in the ovariectomized (OVX) osteoporotic rat model has been monitored using in vitro micro-computed tomography (micro-CT) to assess bone structure (bone volume/total volume, BV/TV). The purpose of this study was to assess the importance of baseline control and sham groups in 12–16-week-old, reproductively mature rats. Measurements were carried out in a longitudinal and age-matched fashion using newer in vivo peripheral quantitative computed tomography (pQCT), which measures apparent bone mineral density (BMD). BMD was measured at the distal femoral metaphysis of 12-week-old female Wistar rats with pQCT. Subsequently, animals were either OVX or sham operated, and pQCT measurements were repeated four weeks later. Then, all rats were euthanized and in vitro BMD and BV/TV were obtained by micro-CT imaging. Results from three consistently differentiated regions of interest showed that there was significant bone loss and growth during the four weeks in the OVX and sham group, respectively. Taking this into account, i.e. a posteriori superimposing growth to loss, no differences resulted between BMD values measured in a longitudinal fashion with pQCT and that measured in comparison with an age-matched sham group with micro-CT and pQCT. In addition, there was a strong linear correlation between BMD measured with pQCT and BV/TV obtained from micro-CT. In conclusion, this outcome provides new insights into individual bone changes due to OVX and growth in Wistar rats during the age period of 12–16 weeks, which is often applied in osteoporosis research as the ‘mature’ rat model. Data can be used as baseline information upon which future in vivo study designs with this rat model can refer to reduce and minimize animal use.

Low-dose X-irradiation promotes mineralization of fracture callus in a rat model

OBJECTIVES

This study investigated the hypothesized beneficial effect of low-dose irradiation (LDI) on fracture callus mineralization in a rat model.

METHODS

Seventy-two male Sprague-Dawley rats were averagely randomized into LDI group (rats treated with LDI) and SHAM group (rats treated with sham irradiation). Right after either LDI or sham irradiation, a standardized closed fracture on the right femur was established. At 2, 3 and 4 weeks postfracture, 12 rats in each group were euthanized. Fracture callus was assessed by using radiography and MicroCT for callus bridging, peripheral quantitative computed tomography (pQCT) for quantifying bone mineral content (BMC) and cross sectional area (CSA), confocal laser scanning microscopy for measuring area fraction of fluorescence labeling (AFFL) and four-point bending test for examining mechanical properties.

RESULTS

The CSA and AFFL were found to be 22 and 33% smaller in the LDI group compared to the SHAM group at 2 weeks (P<0.05 for both), whereas the BMC and AFFL were 15 and 34% higher in the LDI group at 3 weeks (P<0.05 for both). The changing patterns were consistent with the findings in 3-D MicroCT reconstructions. The mechanical parameters (Max-Load, Stiffness and Energy) were also 18, 30 and 24% higher in the LDI group than in the SHAM group at 3 weeks (P<0.05 for all). At 4 weeks, there was no difference found for all assessments between the two groups.

CONCLUSION

The results indicated LDI promoted mineralization at the stage of hard callus formation in a rat fracture model.

Review of nonprimate, large animal models for osteoporosis research

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

An in vitro optimized injectable calcium phosphate cement for augmenting screw fixation in osteopenic goats

This study reports the proportioning and standardized mixing procedures for preparing a hydroxylapatite cement (tetracalcium phosphate and dicalcium phosphate) of desired viscosity and mechanical strength reproducibly for application in trauma surgery. The behavior and the biomechanical properties of the resulting bone cement in screw augmentation were then evaluated in our osteopenic goat model. The use of a shaker standardized the mixing procedure. The optimal volume of Na2HPO4 used to prepare the injectable cement was 0.45 mL/g, with averaged in vitro compressive strength of 48.29 +/- 5.62 MPa. Histology showed increasing tightly-coupled bone apposition on the cement surface without fibrous encapsulation as observed in the screw-only controls with time in the osteopenic goat model. The cement increased the initial screw pull-out force (54.7%, p = 0.005) significantly and the energy required to failure (54.7%, p < 0.05) significantly, and remained higher than the screw-only controls after 3 months (9.8% and 20.2%, respectively) and 6 months (20.2% and 44.7%, respectively). These results imply potential in the prevention of interfacial micromotions and subsequent fibrous tissue formation at the implant-bone interface resulting in a decreased risk of implant failure. The optimized cement in this study may serve as a good candidate for augmenting fixation of osteoporotic bone.

Low-intensity pulsed ultrasound accelerates osteogenesis at bone-tendon healing junction

This study was designed to evaluate low-intensity pulsed ultrasound (LIPUS) in acceleration of mineralization and remodeling of the new bone formed at the healing interface of bone-tendon junction. Thirty-two mature New Zealand white rabbits underwent partial patellectomy and direct repair of the patellar tendon and proximal patella. Animals were then divided into LIPUS treatment group (20 min/d, 5 times/wk) and placebo control group and were euthanized at week 8 and 16 postoperatively (n = 8, for each group and time point). The main outcome measures included new bone size and its bone mineral density (BMD). Results showed that the size of new bone was found to be 2.6 and 3.0 times significantly greater in the LIPUS group compared with that of the control group at weeks 8 and 16, respectively. In addition, the LIPUS group showed significantly higher BMD at week 8 than controls, but not at week 16. In conclusion, this was the first experimental study to show that LIPUS was able to enhance osteogenesis at the healing bone-tendon junction, especially before the postoperative week 8. Findings of this study formed a scientific basis for future clinical trials and establishment of indication of LIPUS for enhancing bone-tendon junction repair.

Relationship between stages of the estrous cycle and bone cell activity in Thoroughbreds

OBJECTIVE

To investigate the relationship between stage of estrous cycle and bone cell activity in Thoroughbreds.

SAMPLE POPULATION

Blood samples collected from forty-seven 2-year-old Thoroughbred mares in training for racing.

PROCEDURES

Blood samples were collected monthly (in April through September) from the mares. Stage of estrus was determined by assessing serum progesterone concentration. Bone cell activity was determined by measuring concentrations of 2 markers of bone formation (osteocalcin and the carboxy-terminal propeptide of type I collagen [PICP]) and a marker of bone resorption (the cross-linked carboxy-terminal telopeptide of type I collagen [ICTP]) in sera.

RESULTS

When the relationship between stage of the estrous cycle and markers of bone cell activity was examined, serum concentrations of both osteocalcin and ICTP were significantly higher in mares that were in the luteal phase, compared with mares that were at other stages of the estrous cycle. Stage of estrus did not affect serum PICP concentration.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate that bone cell activity in Thoroughbred mares fluctuates during the estrous cycle; serum concentrations of markers of bone formation and bone resorption are increased during the luteal phase. Further studies are required to determine whether these changes are of clinical importance and increase the risk of injury for mares in training during the breeding season. As in humans, stage of estrus must be considered as a source of uncontrollable variability in serum bone marker concentrations in horses.

Flavonoids derived from herbal Epimedium Brevicornum Maxim prevent OVX-induced osteoporosis in rats independent of its enhancement in intestinal calcium absorption

AIM

Factorial design was used to test our hypothesis whether a group of flavonoids (FE) derived from herbal Epimedium Brevicornum Maxim exerted its preventive effects on estrogen-deficiency-induced osteoporosis mainly through an enhancement in intestinal calcium absorption.

MATERIALS AND METHODS

Forty-five 12-month-old female Wistar rats were used and randomly assigned into sham-operated group and four ovariectomy (OVX) subgroups, i.e. OVX with vehicle (OVX group), OVX with FE (FE group), OVX with calcium supplement (CS group), and OVX with FE and CS (FE + CS group). Daily oral administration of FE (10 mg/kg/day) and/or CS (56 mg/kg/day) started on day 4 after OVX for 12 weeks. Before sacrificing the animals, urine and serum samples were collected for assaying indicators related to intestinal calcium absorption, regulator for calcium homeostasis, and markers of bone turnover. The left proximal femur was dissected for evaluation of the primary end-point (failure force), the second end-points (pQCT-quantified densitometry, geometry, and micro-CT-quantified 3-D trabecula micro-architecture), and pQCT-defined cross-sectional envelope.

RESULTS

FE was found to be able to prevent OVX-induced reduction in failure force as well as the above second end-points, without resulting in an increased uterus weight. CS had no preventive effect on OVX-induced reduction in failure force. Two-way factorial interaction analysis between FE and CS showed that the un-enhanced suppression of parathyroid hormone for calcium homeostasis did not provide link between the enhanced intestinal calcium absorption and the enhanced inhibition of bone resorption in the present study. Furthermore, the discrepancies between the enhanced intestinal calcium absorption and the un-enhanced end-point measures as well as anabolic effect were also revealed by the interaction analysis.

CONCLUSION

The present study suggested that FE inhibited bone resorption, stimulated bone formation, and accordingly prevented osteoporosis without hyperplastic effect on uterus in the OVX rat model, which was however independent of an enhancement in intestinal calcium absorption.

Trabecular bone status in ultradistal tibia under habitual gait loading: a pQCT study in postmenopausal women

This study investigated regional volumetric trabecular bone mineral density (tBMD) and bone area at the ultradistal tibia in Chinese women using peripheral quantitative computed tomography. Fifty-six postmenopausal women aged 47-62 yr participated in BMD measurements at baseline and 22 of them were followed at both 1-yr and 3-yr follow-up scans. Regional baseline tBMD, rate of annual bone loss, and trabecular bone area were determined. Baseline measurements showed that the tBMD of both the posterior (252.9+/-63.4 mg/cm(3)) and medial (226.6+/-68.9 mg/cm(3)) regions was significantly higher than that of the anterior (126.3+/-61.9 mg/cm(3)) and lateral regions (149.8+/-50.6 mg/cm(3)), respectively (p<0.001). Both the 1-yr and 3-yr follow-up measurements showed that there was significant physiological annual tBMD loss on an average of 1.61%, at the four regions. Inter-slice regional tBMD and trabecular bone area measurements demonstrated a significant linear decrease from the distal to proximal aspects (p<0.001). Findings suggest that dynamic compressive loading during the heel strike and the body weight vector shifting toward the medial aspect during the stance phase in a normal gait might account for the regional tBMD differences. Increased tBMD and bone area toward the distal tibial endplate may adapt to withstand the axial impact loading. However, the low-impact weight-bearing nature of a normal gait may not be osteogenic to prevent regional bone loss. An exercise program specific to the women at risk should be contemplated.

Regional variations in microstructural properties of vertebral trabeculae with structural groups

STUDY DESIGN

Micro-computed tomography (CT) scanning to investigate three-dimensional microstructural properties of L4 vertebral bodies.

OBJECTIVE

To identify the regional variations in the three-dimensional microstructural properties of vertebral cancellous bones with respect to structural types for the prediction of related regional fracture risks.

SUMMARY OF BACKGROUND DATA

The literature contains no reports on regional variations in morphologic properties of vertebral trabeculae with microstructural types, which may shed light on the patterns of osteoporotic fractures.

METHODS

Ninety cubic cancellous specimens were obtained from 6 normal L4 vertebral bodies of 6 male donors 62 to 70 years of age and were scanned using a high-resolution micro-CT system. These specimens were further divided into two groups according to the average structure model index (SMI) of the 15 trabecular specimens in each vertebral body. Adjustment for age differences was done for the microstructural parameters, i.e.-, bone volume fraction, trabecular number, trabecular thickness, structure model index, degree of architectural anisotropy, and connectivity density, to allow investigation on the regional variations in different transverse layers and vertical columns independent of age.

RESULTS

Trabecular specimens with lower mass were liable to form high-SMI group and the differences in all parameters reached significance level either between columns or between layers from two groups.

CONCLUSIONS

The anterior column in the high-SMI group is more susceptible to vertebral body wedge fracture; and in the low-SMI group, off-axis bone damage is most harmful to the central column of vertebral trabeculae. The data obtained may help to identify the most critical locations of fracture risks at an early stage and provide a microstructural basis for the repair and clinical treatment of vertebral fractures.

Phytoestrogen-rich herb formula "XLGB" prevents OVX-induced deterioration of musculoskeletal tissues at the hip in old rats

This study investigated a phytoestrogen-rich herb formula, Xianlinggubao (XLGB) (including genistein 510 microg/g and daidzein 2500 microg/g), concerning prevention of OVX-induced deterioration of musculoskeletal tissues in 11-month-old female Wistar rats, which were randomized into Sham, OVX, and XLGB groups. Daily oral administration of XLGB (250 mg/kg/day) started after OVX for 3 months. mRNA of MHC-I IIa IIb of abductor muscle was determined by RT-PCR. The proximal femoral BMD and geometry, microarchitecture, and mechanical strength were evaluated by pQCT, micro-CT, and compressive testing, respectively. The bone turnover biochemical markers serum osteocalcin (OC) and urinary deoxypyridinoline (DPD) were evaluated. The results showed that (1) XLGB-treated OVX rats showed no difference compared to the Sham group, whereas OVX induced significant deterioration in variables related to bone density, microarchitecture, and mechanical strength (P < 0.05); (2) biochemical markers showed no difference between sham and XLGB groups as compared with higher bone turnover in OVX rats (P < 0.05); (3) mRNA expression of MHC-I IIa IIb was downregulated in OVX rats but upregulated after XLGB treatment (P < 0.05); and (4) as compared with the OVX group, no uterine hypertrophy was found in XLGB-treated rats. In conclusion, findings of this study suggested that the herbal preparation XLGB was able to prevent OVX-induced deterioration of musculoskeletal tissues at the hip without causing uterine stimulation.