Bone Macro Research Articles

Role of resistance training in bone macro and micro damages in an estrogen absence animal model

AimsWe evaluated the effects of resistance training (RT) on bone properties, morphology, and bone extracellular matrix (ECM) remodeling markers in an ovariectomy (OVX) rat model. Main methodsThirty-six female rats were divided into four groups: sham sedentary, OVX sedentary, sham RT, and OVX RT. Rats performed RT for ten weeks, during which they climbed a ladder with progressive loads attached to the tail. Tibias were stored for dual-energy X-ray densitometry (DXA), micro-computed tomography (micro-CT), and biomechanical, biophysical, and biochemical analysis. Femurs were stored for morphological, gene expression, and gelatin zymography analysis. Key findingsOVX decreased bone mineral density, stiffness, maximal load, and calcium content, which was reversed by RT. The trabecular number, connectivity, and MMP-13 gene expression decreased in OVX groups. Furthermore, OVX increased run-related transcription factor-2 (RUNX-2) and osteoprotegerin (OPG) gene expression, and increased the number of adipocytes in bone marrow and MMP-2 activity. SignificanceRT was efficient in preventing or reversing changes in bone biomechanical properties in OVX groups, improving fracture load and resilience, which is relevant to prevent fractures. On the other hand, RT did not decrease the number of bone adipocytes in the OVX-RT group. However, RT was efficient for increasing trabecular thickness and cortical bone volume, which improved bone resistance. Our findings provide further insights into the mechanisms involved in the role of RT in OVX damage protection.

The effects of combined amplitude and high-frequency vibration on physically inactive osteopenic postmenopausal women.

Purpose: To evaluate whole-body vibration (WBV) osteogenic potential in physically inactive postmenopausal women using high-frequency and combined amplitude stimuli. Methods: Two-hundred fifty-five physically inactive postmenopausal women (55–75 years) with 10-year major osteoporotic fracture risk (3%–35%) participated in this 18-month study. For the first 12 months, the vibration group experienced progressive 20-min WBV sessions (up to 3 sessions/week) with rest periods (30–60 s) between exercises. Frequencies (30–50 Hz), with low (0.2–0.4 mm) and high (0.6–0.8 mm) amplitude stimuli were delivered via PowerPlate Pro5 platforms producing accelerations of (0.75–7.04 g). The last 6 months for the treatment group were a follow-up period similar to control. Serum bone remodelling markers [C-terminal crosslinked telopeptide of type-1 collagen (CTX), procollagen type-1 N-terminal propeptide (P1NP), bone alkaline phosphatase (BAP) and sclerostin] were measured at fasting. CTX and P1NP were determined by automated chemiluminescence immunoassay, bone alkaline phosphatase (BAP) by automated spectrophotometric immunoassay, and sclerostin by an enzyme-immunoassay. Bone mineral density (BMD) of the whole-body, proximal femur and lumbar vertebrae was measured by dual-energy X-ray absorptiometry (DXA). Bone microarchitecture of the distal non-dominant radius and tibia was measured by high-resolution peripheral quantitative computed tomography (HR-pQCT). Results: Femoral neck (p = 0.520) and spine BMD (p = 0.444) failed to improve after 12 months of WBV. Bone macro and microstructural parameters were not impacted by WBV, as well as estimated failure load at the distal radius (p = 0.354) and tibia (p = 0.813). As expected, most DXA and HR-pQCT parameters displayed age-related degradation in this postmenopausal population. BAP and CTX increased over time in both groups, with CTX more marginally elevated in the vibration group when comparing baseline changes to month-12 (480.80 pmol/L; p = 0.039) and month-18 (492.78 pmol/L; p = 0.075). However, no differences were found when comparing group concentrations only at month-12 (506.35 pmol/L; p = 0.415) and month-18 (518.33 pmol/L; p = 0.480), indicating differences below the threshold of clinical significance. Overall, HR-pQCT, DXA bone parameters and bone turnover markers remained unaffected. Conclusion: Combined amplitude and high-frequency training for one year had no ameliorating effect on DXA and HR-pQCT bone parameters in physically inactive postmenopausal women. Serum analysis did not display any significant improvement in formation and resorption markers and also failed to alter sclerostin concentrations between groups.

Effect of verapamil on bone mass, microstructure and mechanical properties in type 2 diabetes mellitus rats

BackgroundVerapamil was mainly used to treat hypertension, cardiovascular disease, inflammation and improve blood glucose in patients with diabetes, but its effects on bone mass, microstructure and mechanical properties were unclear. This study described the effects of verapamil on bone mass, microstructure, macro and nano mechanical properties in type 2 diabetic rats.MethodsRat models of type 2 diabetes were treated with verapamil at doses of 4, 12, 24 and 48 mg/kg/day by gavage respectively, twice a day. After 12 weeks, all rats were sacrificed under general anesthesia. Blood glucose, blood lipid, renal function and biochemical markers of bone metabolism were obtained by serum analysis, Micro-CT scanning was used to assess the microstructure parameters of cancellous bone of femoral head, three-point bending test was used to measure maximum load and elastic modulus of femoral shaft, and nano-indentation tests were used to measure indentation moduli and hardnesses of longitudinal cortical bone in femoral shaft, longitudinal and transverse cancellous bones in femoral head.ResultsCompared with T2DM group, transverse indentation moduli of cancellous bones in VER 24 group, longitudinal and transverse indentation moduli and hardnesses of cancellous bones in VER 48 group were significantly increased (p < 0.05). Furthermore, the effects of verapamil on blood glucoses, microstructures and mechanical properties in type 2 diabetic rats were dependent on drug dose. Starting from verapamil dose of 12 mg/kg/day, with dose increasing, the concentrations of P1NP, BMD, BV/TV, Tb. Th, Tb. N, maximum loads, elastic moduli, indentation moduli and hardnesses of femurs in rats in treatment group increased gradually, the concentrations of CTX-1 decreased gradually, but these parameters did not return to the level of the corresponding parameters of normal rats. Verapamil (48 mg/kg/day) had the best therapeutic effect.ConclusionVerapamil treatment (24, 48 mg/kg/day) significantly affected nano mechanical properties of the femurs, and tended to improve bone microstructures and macro mechanical properties of the femurs, which provided guidance for the selection of verapamil dose in the treatment of type 2 diabetic patients.

EFFICACY OF ORAL VITAMIN D SUPPLEMENTATION OR SIMULATED SUNLIGHT ON BONE DURING MILITARY TRAINING

25-hydroxyvitamin D (25(OH)D) ≥50 nmol·L-1 is essential for bone health. Vitamin D deficiency during arduous training has implications for increased stress fracture risk. Vitamin D is mainly synthesised from skin exposure to the sun; around 20% of vitamin D is obtained from the diet. PURPOSE: This study compared the efficacy of vitamin D supplementation by oral pill versus simulated sunlight on bone macro- and micro-architecture during a 13-week military training course in winter. METHODS: Eighty male infantry recruits (mean ± SD, age 22 ± 3 years, height 1.78 ± 0.07 m, body mass 77.9 ± 10.7 kg) received oral vitamin D3 (1,000 IU·D-1 for 4 weeks and then 400 IU·d-1 for 8 weeks, n = 21), an oral placebo (n = 19), solar-simulated radiation (SSR, 1.3 × standard erythemal dose in T-shirt and shorts, 3 d·wk-1 for 4 weeks and 1 d·wk-1 for 8 weeks, n = 22), or placebo SSR (n = 18). Total 25(OH)D was measured by LC-MS/MS in week 1, 5 and 13, and bone density and structure was assessed at the ultra-distal dominant tibia by HR-pQCT (Xtreme CTI, Scanco) in week 1 and 13. RESULTS: Oral vitamin D3 and SSR increased 25(OH)D from week 1 (51 ± 22 and 43 ± 21 nmol·L-1) to week 5 (78 ± 23 and 79 ± 15 nmol·L-1) and week 13 (75 ± 15 and 76 ± 12 nmol·L-1 , P < 0.001). The oral and SSR placebos did not change 25(OH)D from week 1 (51 ± 40 and 41 ± 17 nmol·L-1) to week 5 (45 ± 4 and 41 ± 16 nmol·L-1), but 25(OH)D increased in both groups by week 13 (60 ± 4 and 65 ± 15 nmol·L-1, P ≤ 0.010). Supplementation and training did not affect total, trabecular or cortical volumetric bone mineral density, cortical area, trabecular volume, number or thickness, or cortical pore diameter (main effects of time, P ≥ 0.105; group × time interactions, P ≥ 0.258). Training increased cortical thickness (1.30 ± 0.25 to 1.32 ± 0.25 mm), and reduced trabecular area (682 ± 133 to 680 ± 133 mm2) and spacing (360 ± 58 to 345 ± 71 μm, main effects of time, P ≤ 0.041), but supplementation had no effect (group × time interactions, P ≥ 0.181). There was a significant group × time interaction for cortical perimeter (P = 0.033) and porosity (P = 0.049); training had no effect on either measure for any group (P ≥ 0.068). CONCLUSION: Vitamin D supplementation in winter, using strategies to increase total 25(OH)D above 50 nmol·L-1, exerted no effect on bone macro- or micro-architecture beyond the osteogenic effects of exercise training.

Approach to the knowledge of preservation of pleistocenic bone: The case of a Gomphothere cranium from the site of Tepeticpac, Tlaxcala, Mexico

An almost complete cranium of a gomphoterium found in Tepeticpac, Tlaxcala, was analyzed with X-ray diffraction (XRD), Petrography and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) to stablish the transformations of the bone during its burial. The analyses assessed that the bone mineral (bioapatite) had suffered modifications in mineral composition, “crystallinity index”, cell parameters and CO2 content. However, the paleohistological structure of the bone was not significantly affected, although evidence of microbial attack was found in the bone surfaces. The filling minerals of bone macro and micro porosity were also analyzed; its main filling minerals are calcite (micrite and sparite), clays, and minerals of volcanic origin.

The Impact of Freezing on Bone Mineral Density: Implications for Forensic Research.

It is common for researchers using animal or human remains for scientific study to freeze samples prior to use. However, effects of freezing on bone macro- or microstructure are relatively unknown. The research objective of this study was to determine whether freezing could potentially bias experimental results by analyzing changes in bone mineral density (BMD) with the freezing of remains over time. Eight fetal pigs were scanned to determine their initial BMD before freezing. Three piglets underwent a freeze-thaw cycle to assess the effects of the freezing process. Four piglets were frozen and scanned weekly for 20 weeks to assess freezing over time. The overall average between the fresh initial scan and final frozen scan was significantly different (p < 0.001). Per contra, the final thawed BMD scans did not differ from the initial fresh scan (p = 0.418). Thus, completely thawed remains are recommended for experimental studies.

Changes in bone macro- and microstructure in diabetic obese mice revealed by high resolution microfocus X-ray computed tomography.

High resolution microfocus X-ray computed tomography (HR-microCT) was employed to characterize the structural alterations of the cortical and trabecular bone in a mouse model of obesity-driven type 2 diabetes (T2DM). C57Bl/6J mice were randomly assigned for 14 weeks to either a control diet-fed (CTRL) or a high fat diet (HFD)-fed group developing obesity, hyperglycaemia and insulin resistance. The HFD group showed an increased trabecular thickness and a decreased trabecular number compared to CTRL animals. Midshaft tibia intracortical porosity was assessed at two spatial image resolutions. At 2 μm scale, no change was observed in the intracortical structure. At 1 μm scale, a decrease in the cortical vascular porosity of the HFD bone was evidenced. The study of a group of 8 week old animals corresponding to animals at the start of the diet challenge revealed that the decreased vascular porosity was T2DM-dependant and not related to the ageing process. Our results offer an unprecedented ultra-characterization of the T2DM compromised skeletal micro-architecture and highlight an unrevealed T2DM-related decrease in the cortical vascular porosity, potentially affecting the bone health and fragility. Additionally, it provides some insights into the technical challenge facing the assessment of the rodent bone structure using HR-microCT imaging.

Bone Strength and Structural Deficits in Children and Adolescents With a Distal Forearm Fracture Resulting From Mild Trauma

Although distal forearm fractures (DFFs) are common during childhood and adolescence, it is unclear whether they reflect underlying skeletal deficits or are simply a consequence of the usual physical activities, and associated trauma, during growth. Therefore, we examined whether a recent DFF, resulting from mild or moderate trauma, is related to deficits in bone strength and cortical and trabecular bone macro- and microstructure compared with nonfracture controls. High-resolution peripheral quantitative computed tomography was used to assess micro-finite element-derived bone strength (ie, failure load) and to measure cortical and trabecular bone parameters at the distal radius and tibia in 115 boys and girls with a recent (<1 year) DFF and 108 nonfracture controls aged 8 to 15 years. Trauma levels (mild versus moderate) were assigned based on a validated classification scheme. Compared with sex-matched controls, boys and girls with a mild-trauma DFF (eg, fall from standing height) showed significant deficits at the distal radius in failure load (-13% and -11%, respectively; p < 0.05) and had higher ("worse") fall load-to-strength ratios (both +10%; p < 0.05 for boys and p = 0.06 for girls). In addition, boys and girls with a mild-trauma DFF had significant reductions in cortical area (-26% and -23%, respectively; p < 0.01) and cortical thickness (-14% and -13%, respectively; p < 0.01) compared with controls. The skeletal deficits in the mild-trauma DFF patients were generalized, as similar changes were present at the distal tibia. By contrast, both boys and girls with a moderate-trauma DFF (eg, fall from a bicycle) had virtually identical values for all of the measured bone parameters compared with controls. In conclusion, DFFs during growth have two distinct etiologies: those owing to underlying skeletal deficits leading to fractures with mild trauma versus those owing to more significant trauma in the setting of normal bone strength.

Advanced CT based In Vivo Methods for the Assessment of Bone Density, Structure, and Strength

Based on spiral 3D tomography a large variety of applications have been developed during the last decade to asses bone mineral density, bone macro and micro structure, and bone strength. Quantitative computed tomography (QCT) using clinical whole body scanners provides separate assessment of trabecular, cortical, and subcortical bone mineral density (BMD) and content (BMC) principally in the spine and hip, although the distal forearm can also be assessed. Further bone macrostructure, for example bone geometry or cortical thickness can be quantified. Special high resolution peripheral CT (hr-pQCT) devices have been introduced to measure bone microstructure for example the trabecular architecture or cortical porosity at the distal forearm or tibia. 3D CT is also the basis for finite element analysis (FEA) to determine bone strength. QCT, hr-pQCT, and FEM are increasingly used in research as well as in clinical trials to complement areal BMD measurements obtained by the standard densitometric technique of dual x-ray absorptiometry (DXA). This review explains technical developments and demonstrates how QCT based techniques advanced our understanding of bone biology.

Mechanical torque measurement for in vivo quantification of bone strength in the proximal femur

IntroductionBone strength determines fracture risk and fixation strength of osteosynthesis implants. In vivo, bone strength is currently measured indirectly by quantifying bone mineral density (BMD) which is however only one determinant of the bone's biomechanical competence besides the bone's macro- and micro-architecture and tissue related parameters. We have developed a measurement principle (DensiProbe™ Hip) for direct, mechanical quantification of bone strength within the proximal femur upon hip fracture fixation. Previous cadaver tests indicated a close correlation between DensiProbe™ Hip measurements, 3D micro-CT analysis and biomechanical indicators of bone strength. The goal of this study was to correlate DensiProbe™ Hip measurements with areal bone mineral density (BMD). MethodsForty-three hip fracture patients were included in this study. Intraoperatively, DensiProbe™ Hip was inserted to the subsequent hip screw tip position within the femoral head. Peak torque to breakaway of local cancellous bone was registered. Thirty-seven patients underwent areal BMD measurements of the contralateral proximal femur. Failure of fixation was assessed radio graphically 6 and 12 weeks postoperatively. ResultsPeak torque and femoral neck BMD showed significant correlations (R=0.60, P=0.0001). In regression analysis, areal BMD explained 46% of femoral neck BMD variance in a quadratic relationship. Throughout the 12-week follow-up period, no failure of fixation was observed. ConclusionsDensiProbe™ Hip may capture variations of bone strength beyond areal BMD which are currently difficult to measure in vivo. A multicenter study will clarify if peak torque predicts fixation failure.

Advanced imaging of bone macro and micro structure

Advanced imaging of bone macro and micro structure

Structural Determinants of Vertebral Fracture Risk

Vertebral fractures are more strongly associated with specific bone density, structure, and strength parameters than with areal BMD, but all of these variables are correlated. It is unclear whether the association of areal BMD (aBMD) with vertebral fracture risk depends on bone density per se, bone macro- or microstructure, overall bone strength, or spine load/bone strength ratios. From an age-stratified sample of Rochester, MN, women, we identified 40 with a clinically diagnosed vertebral fracture (confirmed semiquantitatively) caused by moderate trauma (cases; mean age, 78.6 +/- 9.0 yr) and compared them with 40 controls with no osteoporotic fracture (mean age, 70.9 +/- 6.8 yr). Lumbar spine volumetric BMD (vBMD) and geometry were assessed by central QCT, whereas microstructure was evaluated by high-resolution pQCT at the ultradistal radius. Vertebral failure load ( approximately strength) was estimated from voxel-based finite element models, and the factor-of-risk (phi) was determined as the ratio of applied spine loads to failure load. Spine loading (axial compressive force on L3) was similar in vertebral fracture cases and controls (e.g., for 90 degrees forward flexion, 2639 versus 2706 N; age-adjusted p = 0.173). However, fracture cases had inferior values for most bone density and structure variables. Bone strength measures were also reduced, and the factor-of-risk (phi) was 35-37% greater (worse) among women with a vertebral fracture. By age-adjusted logistic regression, relative risks for the strongest fracture predictor in each of the five main variable categories were bone density (total lumbar spine vBMD: OR per SD change, 2.2; 95% CI, 1.1-4.3), bone geometry (vertebral apparent cortical thickness: OR, 2.1; 95% CI, 1.1-4.1), bone microstructure (none significant); bone strength ("cortical" [outer 2 mm] compressive strength: OR, 2.5; 95% CI, 1.3-4.8), and factor-of-risk (phi for 90 degrees forward flexion/overall vertebral compressive strength: OR, 3.2; 95% CI, 1.4-7.5). These variables were correlated with spine aBMD (partial r, -0.32 to 0.75), but each was a stronger predictor of fracture in the logistic regression analyses. The association of aBMD with vertebral fracture risk is explained by its correlation with more specific bone density, structure, and strength parameters. These may allow deeper insights into fracture pathogenesis.

Advanced imaging of bone macro and micro structure

In the past decade, considerable progress has been made in the development of methods for assessing the skeleton noninvasively so that osteoporosis can be detected early, its progression and response to therapy carefully monitored, or the risk of fracture effectively ascertained. Bone mineral density (BMD) of the peripheral, central, or entire skeleton as well as the trabecular or cortical bone envelopes, can now be evaluated with a high degree of accuracy and precision, and the strength of bone and the propensity to fracture can be reliably estimated. Noninvasive and/or nondestructive techniques are capable of providing macro or micro structural information about bone, beyond simple bone densitometry. While the latter provides important information about osteoporotic fracture risk, numerous studies indicate that bone strength is only partially explained by BMD. Quantitative assessment of macrostructural characteristics such as geometry, and microstructural features such as relative trabecular volume, trabecular spacing, and connectivity, may improve our ability to estimate bone strength. The methods available for quantitatively assessing macrostructure include (besides conventional radiographs, which are not considered in this review) computed tomography and particularly volumetric quantitative computed tomography (vQCT). Methods for assessing microstructure of trabecular bone noninvasively and/or nondestructively include high-resolution computed tomography (hrCT), micro computed tomography (mCT), high-resolution magnetic resonance (hrMR), and micro magnetic resonance (mMR). vQCT, hrCT, and hrMR are generally applicable in vivo, and mCT and mMR are principally applicable in vitro.