Marrow Star Volume Research Articles

Glucocorticoid‐induced dose‐related and site‐specific bone remodelling, microstructure, and mechanical changes in cancellous and cortical bones

The study investigated the effects of long-term glucocorticoid (GC) administration on bone remodelling, microstructure, and biomechanical strength in cortical and cancellous (trabecular) bones. Thirty-one female Sprague-Dawley rats were randomly divided into three dexamethasone (Dex) dosage groups, 1.0, 2.5, and 5.0mg/kg twice a week for 8weeks, and one control group treated with saline. At the end of the experiment, the tibia of one side and the fourth lumbar vertebrae were processed into sections for a histomorphometric analysis, while the femur of the same side and the fifth vertebrae were isolated for a biomechanical test. A dose-dependent decline in bone formation was observed in both trabecular and cortical (periosteal and endosteal) bones. In contrast, bone resorption was inhibited only in cancellous bone in the two higher dose groups and not dose-related. The ratio of Node/Termini increased, while marrow star volume (MSV) decreased in all Dex groups in metaphyseal trabecular bones, both of which were dose-dependent. Subendosteal cortex porosity increased in parallel with non-uniform trabecular distribution, but cortical thickness remained unchanged. Interestingly, there were no significant changes in microstructure or mechanical strength in lumbar trabecular bone. The cortical elastic load was dose-independently reduced in all three Dex groups when compared with the control group. In summary, bone remodelling was dose-dependently inhibited in cancellous bones but enhanced in intracortical bones. The non-uniform distribution of trabecular bone and increased porosity in the inner edge of cortical bone were both in parallel with GC dosage, and the porosity increase was more likely to occur, leading to reduced cortical mechanical strength.

Treadmill Running Ameliorates Destruction of Articular Cartilage and Subchondral Bone, Not Only Synovitis, in a Rheumatoid Arthritis Rat Model.

We analyzed the influence of treadmill running on rheumatoid arthritis (RA) joints using a collagen-induced arthritis (CIA) rat model. Eight-week-old male Dark Agouti rats were randomly divided into four groups: The control group, treadmill group (30 min/day for 4 weeks from 10-weeks-old), CIA group (induced CIA at 8-weeks-old), and CIA + treadmill group. Destruction of the ankle joint was evaluated by histological analyses. Morphological changes of subchondral bone were analyzed by μ-CT. CIA treatment-induced synovial membrane invasion, articular cartilage destruction, and bone erosion. Treadmill running improved these changes. The synovial membrane in CIA rats produced a large amount of tumor necrosis factor-α and Connexin 43; production was significantly suppressed by treadmill running. On μ-CT of the talus, bone volume fraction (BV/TV) was significantly decreased in the CIA group. Marrow star volume (MSV), an index of bone loss, was significantly increased. These changes were significantly improved by treadmill running. Bone destruction in the talus was significantly increased with CIA and was suppressed by treadmill running. On tartrate-resistant acid phosphate and alkaline phosphatase (TRAP/ALP) staining, the number of osteoclasts around the pannus was decreased by treadmill running. These findings indicate that treadmill running in CIA rats inhibited synovial hyperplasia and joint destruction.

Zoledronic Acid Reverses Acute Bone Impairment in a Mouse Model for Sickle Cell Disease

Sickle cell disease (SCD) is a worldwide distributed hereditary red cell disorder, characterized by the synthesis of pathological hemoglobin S (HbS). Up to now, limited studies in SCD patients have proposed a bone loss related to recurrent acute vaso-occlusive events (VOCs). Here, we designed a study in a humanized mouse model for SCD to evaluate (i) bone structure turnover and micro-architecture by histomorphometric approach; (ii) osteoblastic differentiation by RT-PCR analysis of bone runx2, sparc and alp gene expression. We used humanized healthy control (Hbatm1(HBA)TowHbbtm3(HBG1,HBB)Tow) and SCD (Hbatm1(HBA)TowHbbtm2(HBG1,HBB*)Tow) mice. Mice were divided into different groups as detailed in the enclosed flow-chart. In steady state, we first evaluated bone-marrow erythropoiesis by FACS analysis based on CD44-TER119 strategy. No signs of ineffective erythropoiesis were detectable in SCD mice compared to controls. Bone analysis was performed by histomorphometric approach after double labelling with demeclocycline followed by calcein to evaluate the dynamic parameters of bone turnover and analyzed by a specific software (bone3.1, Explora Nova, Larochelle, France). The histomorphometric bone analysis revealed (i) reduced bone volume with associated decreased trabecular number and increased trabecular separation; (ii) increased bone-turnover measured as bone formation rate (BFR) and activation frequency (AcF); (iii) decreased number of nodes (NdN) and node termini ratio; (iv) increased marrow star volume (MSV) and fractal dimension (D) compared to healthy mice. The bone molecular analysis revealed a significant down-regulation of runx2, sparc and alp gene expression in SCD mice compared to healthy ones. These data indicate a severe osteoporosis with bone fragility associated with alteration of osteogenic differentiation in SCD mice. Zoledronic acid (Zol) is the most powerful available bisphosphonate used to reduce bone turnover and bone fragility. Since VOCs are life-threatening complication of SCD and mainly involved skeletal system, requiring multidiscliplinary approach, we exposed SCD and control mice to hypoxia/reoxygenation (H/R) stress to mimic acute VOCs (see flow-chart). Mice were exposed to hypoxia (8% oxygen, 10 hours) followed by reoxygenation (21% oxygen) for either 18 hours to carry out molecular analysis or 10 days to carry out histomorphometric analysis. In H/R exposed vehicle treated SCD mice, we found (i) a significant increase in AcF (bone turnover), without differences in bone structure and microarchitecture compared to SCD mice under normoxia; (ii) a further reduction in osteogenic differentiation molecular markers. Zol (100 μg/ Kg in a single ip injection) was administrated either 7 days before (Zol-pre) or immediately after (Zol-post) H/R stress. In SCD mice, both Zol-pre and Zol-post significantly prevented the H/R induced increased bone turnover, while no differences were detectable in bone structure and microarchitecture compared to vehicle treated H/R SCD mice. The molecular analysis showed that Zol increased the osteogenic related gene expression, indicating a positive induction of osteogenic differentiation. Our data suggest that murine SCD is characterized by a significant bone impairment related to the unbalance between osteoblastic/osteoclastic activity in favor of osteoclastic one in presence of a down-regulation of osteogenic differentiation. In SCD, Zol plays a pivotal role decreasing osteoclastic activity and promoting osteogenic differentiation, representing a powerful new therapeutic strategy to limit bone disease in SCD. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Multidetector-row computed tomography is useful to evaluate the therapeutic effects of bisphosphonates in glucocorticoid-induced osteoporosis

Osteoporosis is one of the major complications of glucocorticoid therapy. Osteoporosis is usually defined by the levels of bone mineral density (BMD) assessed by dual energy X-ray absorptiometry (DEXA); however, glucocorticoids often induce fractures in patients with normal BMD. Thus, novel diagnostic approaches are required. In this study, we examined whether multidetector-row computed tomography (MDCT) is useful to assess the bone status in glucocorticoid-induced osteoporosis (GIO). Because bisphosphonates have been proven to prevent bone fracture in GIO, we tried to detect the therapeutic effects of bisphosphonates in GIO by MDCT. Fifteen Japanese patients with immunoglobulin A nephropathy who had normal renal function were enrolled in this open-label randomized trial. Patients were randomly divided into three groups-calcitriol (VD), menatetrenone (VK), or bisphosphonate (Bis). Bone conditions were analyzed twice by three different methods-bone turnover markers, DEXA, and MDCT-at the start and 6 months after the start of therapy. Both bone markers and DEXA could not detect significant differences among the therapeutic groups; however, MDCT-based analyses detected the preventive effects of bisphosphonates in GIO. Compared to VD, Bis improved structural indices, such as bone volume fraction, trabecular separation, marrow star volume, and structure model index whereas the difference between VD and VK was not significant. Finite element analysis revealed that simulated fracture load in the Bis group was significantly improved. These findings suggested that MDCT-based assessment is superior to bone markers and/or DEXA in assessing the therapeutic effect of bisphosphonates on GIO.

The Beneficial Use of Nigella Sativa Powder in the Healing of Different Portions of Extracted Tooth Socket: In Vivo Study

Bac k ground: Nigella sativa is so beneficial due to it’s content of over a hundred components such as aromatic oils, trace elements, vitamins and enzymes. It contains 58% of essential fatty acids including omega 6 and omega 3. These are necessary for the forming of Prostaglandin E1 which balances and strengthens the immune system giving it the power to prevent infections and allergies and control chronic illnesses. Blackseed oil also contains about 0.5 - 1.5% volatile oils including nigellone and thymochinone which are responsible for its anti-histamine, anti-oxidant, anti-infective and broncho-dilating effect. Aim o f the study: To evaluate the effect of Nigella sativa (powder and oil) on the healing process in different portions of rabbit socket by histomorphometric analysis of bone architecture parameters. Mat erials and Methods: The sample of the study consist of twenty rabbits, extract their upper two central incisors under general anesthesia. The left side filled once with Nigella sativa powder and once with Nigella sativa oil material, and the right side left for normal healing as a control group. The two sockets were sutured. The results were studied in intervals period 2 and 6 weeks, histologically and then assayed for histomorphometic analysis for trabecular width, trabecular number and the trabecular separa- tion Marrow space star volume analysis (V*m), Osteoblast, osteocyte, and blood vessels number, in coronal, middle and apical portions of extracted tooth socket. These parameters are derived from microscopic two dimension image measurements analyzer software program. Results: Histomorphometric analysis for variables of trabeculae width (thickness of trabeculae), trabecular separation and cortical thickness in three studied groups for coronal, middle and apical portions of socket showed significant differences in NgS powder and oil groups in comparison to control. Bone marrow star volume showed a significant variation between NgS powder and NgS oil in comparison to control, also bone marrow star volume showed decrease in it’s value with increment in healing period in all groups. Trabecular number and width shows to be higher in NgS powder group in all portions of the socket in comparisum to control and NgS oil groups at 2 and 6 weeks duration. Blood vessels’ number shows to be higher in middle portion in NgS powder group at 2 and 6 weeks duration in comparisum to NgS oil and control groups. Con clusion: Nigella sativa powder suggest to be more effective and enhancer in acceleration of bone formation than oil.

Histomorphometric analysis of bone architecture parameters in socket of rabbit treated with Nigella Sativa

Background: Seeds of Nigella sativa are frequently used in folk medicine in the Middle East and some Asian countries for the promotion of good health and treatment of many ailments. The multiple uses of Nigella sativa in folk medicine encouraged many investigators to isolate the possible active components and to conduct in vivo and in vitro studies on laboratory animals and human beings in order to understand its therapeutic actions. The aim of this study is to evaluate the effect of Nigella Sativa when used as a powder and during oil application on healing process of extracted teeth sockets in different weeks. Materials and Methods: The sample of our study consists of Forty eight rabbits to extract their upper two central incisors under general anesthesia. The left side filled once with Nigella sativa powder and once with Nigella sativa oil material, and the right side left for normal healing as a control group. The two sockets were sutured. The results were studied in intervals period 1, 2, 4, and 6 weeks, histologically and radiographically. Results: Histomorphometric analysis for variables: trabecular width, trabecular number, trabecular separation, Marrow space star volume analysis, Osteoblast number, osteocyte number and blood vessels number for two sockets showed significant differences in NgS powder group in comparison to NgS oil group and both NgS groups in comparison to control. Bone marrow star volume showed a significant variation between NgS powder and NgS oil and in both NgS groups in comparison to control, also bone marrow star volume showed decrease in it’s value with increment in healing period in all groups, Cortical bone thickness records showed increment in NgS powder group in comparison to oil and in both groups in comparison to control with increment in periods of healing, Counting of osteoblast and osteocyte showed high number in both NgS (powder and oil) groups in comparison to control group. The increment in number detected in 2nd week and then decrease as increase in periods (4th and 6th weeks) and numerous blood vessels detected in 4th week’s duration in NgS powder groups in apical portion while it detected in 6th weeks in apical portion for oil group. Conclusion: Nigella sativa (powder or oil) seems to be bioactive materials that enhance differentiation and proliferation of progenitor cells to specialized bone formative cells, with acceleration of bone formation. (J Bagh Coll Dentistry 2012;24(1):45-51).

Vertebral fractures are associated with increased cortical porosity in iliac crest bone biopsy of men with idiopathic osteoporosis

In men, vertebral fractures are poorly associated with bone density, and both cortical and trabecular micro-architectural changes could contribute to bone fragility. Bone histomorphometry makes it possible to investigate both the thickness and porosity of cortical bone, which has been reported to have a major impact on the biomechanical properties of bone. We therefore conducted a cross sectional study using iliac crest biopsies to investigate the trabecular and cortical bone structure in men with or without vertebral fractures. We selected 93 bone biopsies from men with idiopathic osteoporosis (defined as a T-score <− 2.5), between 40 and 70 years of age. Patients were divided into two groups on the basis of the presence ( n = 46) or absence ( n = 47) of prevalent vertebral fracture (VFX). We measured micro-architectural indices in trabecular and cortical bone by histomorphometry at the iliac crest. Patients with VFX had lower trabecular bone volume (BV/TV: 12.4 ± 3.8 versus 14.7 ± 3.1 % (m ± SD)), p < 0.01), higher trabecular separation (Tb.Sp: 871 ± 279 versus 719 ± 151 μm, p < 0.01), and higher marrow star volume (V⁎ m.space: 1.617 ± 1.257 versus 0.945 ± 0.466 mm 3, p < 0.01). Cortical thickness (Ct.Th) was the same in patients with or without VFX, whereas cortical porosity (Ct.Po) was higher in patients with VFX (6.5 ± 2.6 versus 5.0 ± 2.0 %, p < 0.01), because their Haversian canals had higher mean areas (8291 ± 4135 versus 5438 ± 2809 μm 2, p < 0.001). There was no correlation between any trabecular and cortical micro-architectural parameters. Using a logistic regression model, we evaluated the VFX as a function of the V⁎ m.space and Ct.Po, adjusted for age. The odds-ratio of having a VFX was 3.89 (95% CI 1.19–12.7, p = 0.02) for the third tertile of V⁎ m.space (adjusted on age and Ct.Po), and 4.07 (95% CI 1.25–13.3, p = 0.02) for the third tertile of Ct.Po (adjusted on age and V⁎ m.space). Our data show that both trabecular and cortical bone microarchitecture contribute independently to vertebral fractures in men with idiopathic osteoporosis. In contrast to data reported in women, in men it is cortical porosity, and not cortical width, that is associated with vertebral fractures. This suggests that the cortical deficit is different in men and in women with fragility fractures.

Cortical and trabecular bone distribution in the femoral neck in osteoporosis and osteoarthritis

The increased hip fragility in osteoporosis has been attributed mainly to a thinning of the cortex. In contrast, hip arthritis (OA) is not associated with increased risk of hip fracture. The purpose of this study was to assess cortical and trabecular bone structures and their possible regional variability in the femoral neck taken from patients who sustained an osteoporotic hip fracture (OP) compared with patients with OA. We compared the distribution of bone in the ultradistal femoral neck in 21 postmenopausal women with OA (mean age: 66 ± 7.8 years) and 20 postmenopausal women with an osteoporotic hip fracture (OP) (mean age: 79.5 ± 1.9 years). Controlateral hip osteoporosis or osteopenia was confirmed in OP by DEXA ( T-score: − 2.5 ± 0.8 in OP; − 0.9 ± 1.3 in OA). Histomorphometric parameters of bone structure, architecture and connectivity were measured on sections from the ultradistal part of the femoral neck, divided in 4 quadrants. When compared to OA, cortical thickness was significantly decreased in OP ( p < 0.0005) but was the highest in the inferior part in both groups. Cortical porosity was higher in OA (13.48 ± 1.02 and 8.4 ± 1.07% in OA and OP respectively). Compared to OA, the trabecular bone volume was decreased by 50% in OP ( p < 0.0001) with a diminution of the trabecular number ( p < 0.01) and thickness ( p < 0.0001). In parallel, OP group was characterized by a poor connectivity evaluated by the decreased number of nodes ( p < 0.0001), higher trabecular bone pattern factor ( p < 0.0001) and greater marrow star volume ( p < 0.0001). The connectivity was the lowest in the inferior quadrant in OP but not in OA. Our data suggest that in addition to the cortical thinning, the loss of the trabecular bone mass and connectivity plays a role in the skeletal fragility associated with hip fracture. Furthermore, the spatial distribution of the trabeculae differs between OP and OA whereas cortical thinning is homogenous.

Trabecular bone microarchitecture in mild primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) is a common endocrine disease. High levels of PTH cause demineralization of bone and increased risk of fracture. On the other hand, the effect of PHPT on bone structure is more ambiguous. The aim of this study was to evaluate the effect of PHPT on cancellous bone volume, structure, and microarchitecture. Thirteen transiliac biopsy specimens taken in untreated post-menopausal women aged 65+/-5 yr with primary hyperparathyroidism were compared with 13 biopsies taken in normal women aged 66+/-6 yr. None of the patients presented any other disorder affecting bone metabolism. In these samples we evaluated the direct and indirect histomorphometric parameters of bone microarchitecture using an image analysis system consisting of an epifluorescent microscope (Leica DMR) connected to an analogic 3 CCD camera (Sony DXC 390P) and a computer equipped with specific software for histomorphometric analyses. No significant differences between PHPT patients and controls in cancellous bone volume, trabecular thickness, and number were found. Two-dimensional parameters showed a preserved microarchitecture in PHPT patients. On the other hand, indirect parameters of microarchitecture [Marrow Star Volume (MSV) and Trabecular Bone Pattern Factor (TBPf)] showed a significant compromising of microarchitecture in these patients. PHPT patients have similar structural parameters to normal subjects. Concerning microarchitecture, indirect approach by MSV and TBPf shows a significant compromising of connectivity. These results can explain trabecular fragility observed in clinical studies on PHPT.

Preservation of thoracic spine microarchitecture by alendronate: Comparison of histology and microCT

The effect of bisphosphonates on trabecular microarchitecture may contribute to the reduced risk of vertebral fracture with treatment independent of the bone volume. Trabecular structure was examined at the twelfth thoracic vertebra after 2 years of treatment of two groups of ovariectomized baboons on high and low doses of alendronate, compared with ovariectomized and non-ovariectomized controls. Standard 2D histological measurements showed that alendronate treatment of ovariectomized animals resulted in significantly higher total trabecular length and a lower marrow star volume in comparison with ovariectomized controls indicating preservation of connectivity. Similarly when the vertebrae were examined using a novel thick slice technique that combines 2D and 3D information, ovariectomy produced a significantly higher number of “real“ trabecular termini in comparison with normal. When ovariectomized animals were treated with increasing doses of alendronate, fewer “real” termini were seen. MicroCT analysis (2D and 3D) correlated well with the histological measurements, although more variability and less discrimination between groups was seen, with no statistically significant differences with alendronate treatment. Reduced vertebral fracture risk with alendronate may be due to a combination of factors including the increased bone volume, reduced turnover and greater mineralization reported by others. Added to this is now suggested the preservation of several aspects of vertebral cancellous architecture, with microscopy the most sensitive method of analysis.

Evaluation and Development of Automatic Two-Dimensional Measurements of Histomorphometric Parameters Reflecting Trabecular Bone Connectivity: Correlations with Dual-Energy X-Ray Absorptiometry and Quantitative Ultrasound in Human Calcaneum

In osteoporosis, bone fragility results from both bone loss and changes in trabecular microarchitecture, which can be quantified by bone histomorphometric parameters. Twenty human calcaneum were collected after necropsy. All measurements were performed at the same anatomical location. Bone histomorphometric parameters were measured on histological slides with an automatic image analyzer. The aims of our study were (1) to develop automatic measurements of four additional parameters reflecting trabecular network connectivity and complexity, i.e., trabecular bone pattern factor (TBPf), Euler number/tissue volume (Euler) according to the three definitions previously reported and to a fourth one established in the laboratory (Euler(strut.cavity)), marrow star volume, and interconnectivity index, and to determine their usefulness in microarchitecture characterization; and (2) to validate these parameters by evaluating their relationship with dual-energy X-ray absorptiometry and quantitative ultrasound (QUS) measurements performed on the same samples. The statistical analysis showed that TBPf and Euler(strut.cavity) appeared to be the most significant connectivity parameters, independently of bone quantity (bone mineral density, apparent density, cancellous bone volume). For QUS, after adjustment for bone quantity, only speed of sound (SOS) was significantly and negatively correlated to Euler(strut.cavity). Broadband ultrasound attenuation depends only on bone quantity. In conclusion, TBPf (a strut analysis parameter extrapolable in three dimensions) and Euler(strut.cavity) (the only bone connectivity parameter reflecting SOS) are two valid bone microarchitecture parameters. These new parameters were significantly correlated to the established trabecular structure parameters: trabecular thickness or trabecular spacing, being weakly correlated with SOS.

Early Changes in Biochemical Markers of Bone Formation Correlate with Improvements in Bone Structure during Teriparatide Therapy

Biochemical markers of bone turnover may reflect bone structure during anabolic treatment. The objective was to evaluate associations between changes in biochemical markers and structural and dynamic bone parameters during teriparatide treatment. This study was a randomized, multicenter, double-blind, placebo-controlled fracture prevention trial, with 20-month median treatment duration for biopsy subset. The trial was conducted at 11 clinical study sites. Sixty-one postmenopausal women with osteoporosis who had paired transiliac biopsy specimens participated in the study. Once-daily sc injections of either placebo or teriparatide (20 or 40 microg) were administered. The study measured: 1) serum and urinary biochemical markers of bone formation [bone alkaline phosphatase and procollagen I C-terminal propeptide (PICP)] and resorption (N-telopeptide and deoxypyridinoline); and 2) structural and dynamic analyses of bone biopsies, including two-dimensional (2D) histomorphometry and three-dimensional (3D) micro-computed tomography evaluations measured at baseline (n = 57) and 12 (n = 21) or 22 (n = 36) months. U-N-telopeptide/creatinine and serum-PICP correlated with bone structure and dynamic indices at baseline, respectively. Changes in bone alkaline phosphatase at 1 month correlated with changes at 22 months in 2D wall thickness (r = 0.73; P = 0.001), trabecular bone volume (trabecular bone volume per total volume, BV/TV) (r = 0.58; P < 0.05), marrow star volume (r = -0.51; P = 0.05); 3D trabecular thickness (r = 0.49; P < 0.05), and BV/TV (r = 0.54; P < 0.05). Changes in PICP at 1 month correlated with changes in wall thickness (r = 0.60; P = 0.01), and 2D BV/TV (r = 0.51; P < 0.05) at 22 months. Changes in markers at 6 or 12 months were not associated with changes in structural or dynamic parameters. Early (1-month) changes in biochemical markers of bone formation, but not resorption, correlated with improvements in bone structure after 22 months of teriparatide therapy.

Risedronate preserves bone architecture in postmenopausal women with osteoporosis as measured by three-dimensional microcomputed tomography

The deterioration of trabecular microarchitecture induced by elevated bone turnover is increasingly recognized as a factor in the pathogenesis of osteoporotic fractures. We investigated the effect of the reduction of turnover with risedronate on trabecular architecture in postmenopausal women with osteoporosis. Iliac crest bone biopsy specimens taken before and after 3 years of treatment from patients receiving risedronate 5 mg daily (n = 21) or placebo (n = 17) were analyzed using 3-D microcomputed tomography. We found a significant correlation between baseline bone turnover and bone loss in the placebo group, providing evidence that higher turnover induced higher bone loss leading to a greater degree of architectural degradation. When patients were classified into two groups based on baseline bone turnover (MS/BS less than or greater than the median value for the entire cohort), significant decreases in trabecular bone volume (BV/TV, P = 0.009) and trabecular thickness (Tb.Th*, P = 0.008) and an increase in marrow star volume (Ma.St.V, P = 0.008), a measure of trabecular porosity, were observed in the higher turnover (MS/BS> median) placebo-treated patients. The trabecular structure shifted from plates to rods as shown by an increase in structure model index (SMI, P = 0.028) and bone surface to bone volume ratio (BS/BV, P = 0.006). The changes from baseline in the lower turnover (MS/BS<median) placebo patients were variable and not statistically significant. In the risedronate group, the bone volume and the architectural parameters did not change significantly from baseline values in either the higher or the lower turnover groups. Comparing the pair-wise changes from baseline in the higher turnover group, the placebo group experienced decreases in BV/TV (P = 0.071) and Tb.Th* (P = 0.012), and increase in Ma.St.V (P = 0.043), compared to the risedronate-treated women. Also, in comparison to the risedronate group, the trabecular structures in the placebo group were more rod-like, indicated by higher SMI (P = 0.009) and BS/BV (P = 0.02). The results demonstrated that trabecular architecture deteriorated significantly in the placebo-treated women who had higher bone turnover at baseline, and this deterioration was prevented by 3 years of risedronate treatment, presumably because of the reduction in bone turnover. The preservation of architecture may be a contributory mechanism by which risedronate reduces the risk of vertebral fractures in osteoporotic women.

Risedronate Preserves Bone Architecture in Early Postmenopausal Women In 1 Year as Measured by Three-Dimensional Microcomputed Tomography

Risedronate reduces the risk of vertebral fractures by up to 70% within the first year of treatment. Increases in bone mineral density or decreases in bone turnover markers explain only a portion of the anti-fracture effect, suggesting that other factors, such as changes in trabecular bone architecture, also play a role. Our objective was to determine the effects of risedronate on bone architecture by analyzing iliac crest bone biopsy specimens using three-dimensional microcomputed tomography (3-D micro CT). Biopsy specimens were obtained at baseline and after 1 year of treatment from women enrolled in a double-blind, placebo-controlled study of risedronate 5 mg daily for the prevention of early postmenopausal bone loss. Trabecular architecture deteriorated in the placebo group (n = 12), as indicated by a 20.3% decrease in bone volume (25.1% vs. 20.0%, P = 0.034), a 13.5% decrease in trabecular number (1.649 vs. 1.426 mm(-1), P = 0.052), a 13.1% increase in trabecular separation (605 vs. 684 microm, P = 0.056), and an 86.2% increase in marrow star volume (3.251 vs. 6.053 mm(3), P = 0.040) compared with baseline values. These changes in architectural parameters occurred in the presence of a concomitant decrease from baseline in lumbar spine bone mineral density (-3.3%, P = 0.002), as measured by dual energy x-ray absorptiometry. There was no statistically significant ( P < 0.05) deterioration in the risedronate-treated group (n = 14) over the 1-year treatment period. Comparing the actual changes between the two groups, the placebo group experienced decreases in bone volume (placebo, -5.1%; risedronate, +3.5%; P = 0.011), trabecular thickness (placebo, -20 microm; risedronate, +23 microm; P = 0.032), and trabecular number (placebo, -0.223 mm(-1); risedronate, +0.099 mm(-1); P = 0.010), and increases in percent plate (placebo, +2.79%; risedronate, -3.23%; P = 0.018), trabecular separation (placebo, +79 microm; risedronate, -46 microm; P = 0.010) and marrow star volume (placebo, +2.80 mm(3); risedronate, -2.08mm(3); P = 0.036), compared with the risedronate group. These data demonstrate that trabecular architecture deteriorated significantly in this cohort of early postmenopausal women, and that this deterioration was prevented by risedronate. Although there is no direct link in this study between fracture and preservation of architecture, it is reasonable to infer that the preservation of bone architecture may play a role in risedronate's anti-fracture efficacy.

Evidence for an extensive collagen type III proximal domain in the rat femur: II. Expansion with exercise

Exercise in youth may affect bone “quality” as well as quantity. Using the rat model, 1.5-month-old females were divided into four weight-matched groups, exercised short-term (6 weeks, E s, n = 20) and long-term (14 weeks, E L, n = 10) by access to monitored running wheels, and corresponding “sedentary” controls (S S short-term, n = 20; S L long-term, n = 10). Femora were either plastic-embedded or fresh-frozen. Transverse histological slices, 100 μm thick, were cut midshaft, while similar cryosections, 8 μm thick, were prepared from the same site and also coronal to the femoral neck region. An image analyser measured femoral neck and midshaft microarchitecture, while immunostaining localized collagen type III-rich fibres (CIII, an index of Sharpey fibre insertions) and osteopontin-rich osteons (OPN, an index of remodelling). Exercise increased cortical bone (proximal width +18%, midshaft area +7%). It also raised cancellous bone volume (+25%) by trabecular thickening (+30%) with more intraosseous vascularity and new trabecular interconnections (node-terminus ratio, +57%; trabecular pattern factor, −147%; marrow star volume. −48%). In the cortex a prominent discrete subperiosteal domain became wider (+50% midshaft) with exercise and contained more numerous (+15%) CIII-stained fibres. In contrast the encircled inner bone developed more numerous (+14%) OPN-rich osteons. It is concluded that short-term voluntary exercise augments both cortical and cancellous microarchitecture. It also alters protein composition, such that expanding arrays of Sharpey’s fibres within a circumferential proximal domain (Part I) interconnect more powerfully with the musculature and interface more robustly with the core bone that in response becomes more vascular and biodynamic, providing further insight into how muscle mass may be skeletally translated.

Risedronate preserves trabecular architecture and increases bone strength in vertebra of ovariectomized minipigs as measured by three-dimensional microcomputed tomography.

Risedronate reduces the risk of new vertebral fractures up to 70% within 1 year of treatment in patients with osteoporosis. Both increases in bone mass and preservation of bone architecture are thought to contribute to antifracture effects. Our objectives were to determine the effects of risedronate on trabecular bone mass and architecture and to determine the relative contributions of mass and architecture to strength in the vertebra of ovariectomized (OVX) minipigs. The minipigs were OVX at 18 months of age and were treated daily for 18 months with either vehicle or risedronate at doses of 0.5 mg/kg per day or 2.5 mg/kg per day. The three-dimensional (3D) bone architecture of the L4 vertebral cores of Sinclair S1 minipigs was evaluated by 3D microcomputed tomography (muCT). Compared with the OVX control, the vertebral bone volume (bone volume/tissue volume [BV/TV]) was higher in both treated groups (p < 0.05). The architectural changes were more significant at the 2.5-mg/kg dose and were more prevalent at the cranial-caudal ends compared with the midsection. At the higher dose, the trabecular thickness (Tb.Th), trabecular number (Tb.N), and connectivity were higher, and marrow star volume (Ma.St.V) and trabecular separation (Tb.Sp) were lower (p < 0.05). The trabecular separation variation index (TSVI), a new measure to approximate structural variations, was smaller in the 2.5-mg/kg-treated group (p < 0.05). In this group, a significant preservation of trabeculae orthogonal to the cranial-caudal axis was confirmed by a decrease in the degree of anisotropy (DA) and an increase in the percent Cross-strut (% Cross-strut; p < 0.05). Both normalized maximum load (strength) and normalized stiffness of the same vertebral cores were higher in the 2.5-mg/kg risedronate group compared with the OVX group (p < 0.05). BV/TV alone could explain 76% of the variability of the bone strength. The combination of bone volume and architectural variables explained >90% of the strength. The study showed that risedronate preserved trabecular architecture in the vertebra of OVX minipigs, and that bone strength is tightly coupled to bone mass and architecture.

Bone microarchitecture and mechanical resistance

Although bone mass is the main determinant of bone mechanical resistance, it explains only 30 to 40% of the variability of this characteristic, indicating that other factors are involved. Among these factors is bone tissue quality, which depends on bone mineralization, bone turnover, and bone microarchitecture. Several parameters for characterizing bone microarchitecture have been developed over the last 15 years. The simplest (Parfitt’s parameters) are trabecular count, width, and separation. A binary image (two levels of gray) of bone tissue can be expanded and used to determine the trabecular bone pattern factor. This method tends to overestimate the number of convex surfaces, which are characteristic of trabecular network disruption. The binary image can be further simplified (skeletonized) and used to count the number of nodes (anastomoses between trabeculae) or free ends (segments disconnected from the network). The bone marrow star volume, the marrow interconnectivity index, and the Euler-Poincaré number are useful for characterizing the bone marrow. These parameters can be measured on bone specimens or on computed tomography (CT) or magnetic resonance imaging (MRI) scans, although in-plane resolution is far lower with scans than with specimens. Two-dimensional analysis is widely used, although three-dimensional studies are more satisfactory. Finally, fractal analysis is an original approach in which fractal dimension measurement, which is fairly simple, is used to determine the degree of network disruption. Ex vivo histomorphometric data suggest that microarchitecture-related factors may explain 10 to 30% of the variability in bone mechanical resistance beyond the proportion explained by bone mass. Similar results have been obtained in microimaging, CT, and MRI studies. Discrepancies across studies exist, however, in the strength of the relationship between bone mass and bone mechanical resistance; they are probably ascribable to differences in measurement sites and to errors in the measurement of variables characterizing bone mechanical resistance. The finite element method may be a means of sidestepping these problems. It can be used, in particular, to calculate Young’s modulus of elasticity from three-dimensional bone segment reconstructions. The results of the few studies of the finite element method are promising but require confirmation. Finally, a more clinical approach consists in comparing bone architecture in patients with osteoporotic fractures and in controls matched on bone mass. A few cross-sectional studies have used this approach. Bone architecture was evaluated using histomorphometry, CT, or MRI. The results indicate that trabecular network disruption is more severe in patients with than without fractures.

Comparison of Trabecular Bone Microarchitecture and Remodeling in Glucocorticoid-Induced and Postmenopausal Osteoporosis

Long-term treatment with glucocorticoids (GCs) leads to a rapid bone loss and to a greater risk of fractures. To evaluate the specific effects of this treatment on cancellous bone remodeling, structure, and microarchitecture, we compared 22 transiliac biopsy specimens taken in postmenopausal women (65 +/- 6 years) receiving GCs (> or = 7.5 mg/day, for at least 6 months) and 22 biopsy specimens taken in age-matched women with postmenopausal osteoporosis (PMOP), all untreated and having either at least one vertebral fracture or a T score < -2.5 SD. On these biopsy specimens, we measured static and dynamic parameters reflecting trabecular bone formation and resorption. Also, we performed the strut analysis and evaluated the trabecular bone pattern factor (TBPf), Euler number/tissue volume (E/TV), interconnectivity index (ICI), and marrow star volume (MaSV). Glucocorticoid-induced osteoporosis (GIOP), when compared with PMOP, was characterized by lower bone volume (BV/TV), trabecular thickness (Tb.Th), wall thickness (W.Th), osteoid thickness (O.Th), bone formation rate/bone surface (BFR/BS), adjusted mineral apposition rate/bone surface (Aj.AR/BS), and higher ICI and resorption parameters. After adjustment for BV/TV, the W.Th remained significantly lower in GIOP (p < 0.0001). The active formation period [FP(a+)] was not different. Patients with GIOP were divided into two groups: high cumulative dose GCs (HGCs; 23.7 +/- 9.7 g) and low cumulative dose GCs (LGCs; 2.7 +/- 1.2 g). HGC when compared with LGC was characterized by lower W.Th (p < 0.05), BV/TV (p < 0.001), Tb.Th (p < 0.05), trabecular number (Tb.N; p < 0.05), FP(a+)(p < 0.05), and nodes (p < 0.05), and higher E/TV (p < 0.05), ICI (p < 0.005), and TBPf (p < 0.05). When HGC was compared with PMOP, the results were similar except for the MaSV, which was significantly higher (p < 0.005). In summary, GIOP was characterized by lower formation and higher resorption than in PMOP, already present after LGC. With HGCs, these changes were associated with a more dramatic bone loss caused by a major loss of trabecular connectivity.

Evaluation of Changes in Trabecular Bone Architecture and Mechanical Properties of Minipig Vertebrae by Three-Dimensional Magnetic Resonance Microimaging and Finite Element Modeling

The study objective was to analyze the three-dimensional (3D) trabecular architecture and mechanical properties in vertebral specimens of young and mature Sinclair minipigs to assess the relative contribution of architecture to bone strength. We used 3D magnetic resonance microimaging (MRmicroI) and direct image analysis to evaluate a set of standard structural measurements and new architectural descriptors of trabecular bone in biopsy specimens from L2, L3, and L4 vertebrae (n = 16 in each group) from young (mean age, 1.2 years) and mature (mean age, 4.8 years) minipigs. The measurements included bone volume/tissue volume (BV/TV), marrow star volume (Ma.St.V), connectivity density (ConnD), and two new parameters, percent platelike trabeculae (% plate) and percent bone in the load direction (% boneLD). The % plate, calculated from surface curvature, allowed the delineation of plates from rods. The % boneLD quantified the percentage of bone oriented along the long axis of the vertebral body. We showed that 3D MRmicroI can detect the subtle changes in trabecular architecture between the two age groups. ConnD, star volume, % plate, % boneLD, and BV/TV were found to be more effective than the model-based, derived indices (trabecular thickness [Tb.Th], trabecular separation [Tb.Sp], and trabecular number [Tb.N]) in differentiating the structural changes. BV/TV, % plate, and % boneLD significantly increased (p < 0.05) in all three vertebral sites of the mature minipigs. The significant decrease in ConnD and star volume in the mature vertebra was consistent with the concurrent increase of platelike trabecular bone (p < 0.05). Overall, ConnD, star volume, % plate, and % boneLD provided a coherent picture of the architectural changes between the two age groups. Apparent modulus and maximum stress were determined experimentally on biopsy specimens from L2 vertebrae (n = 16). When apparent modulus was predicted using 3D MRmicroI data sets as input for finite element modeling (FEM), the results were similar to the experimentally determined apparent modulus (p = 0.12). Both methods were then used to compare the young and the mature animals; the experimental and predicted apparent modulus were significantly higher for the mature group (p = 0.003 and 0.012, respectively). The experimental maximum stress in the vertebra of the mature animals was twice as high as that for the young animals (p = 0.006). Bone quantity (BV/TV or bone mineral content [BMC]) alone could explain approximately 74-85% of the total variability in stress and modulus. The inclusion of either ConnD or % boneLD with BV/TV in a multiple regression analysis significantly improved the predictability of maximum stress, indicating that architecture makes additional contributions to compressive strength in normal minipig vertebra.

Trabecular architecture in women and men of similar bone mass with and without vertebral fracture: I. two-dimensional histology

While osteoporosis is characterized by a low bone mass there is a well-recognized overlap in bone mineral density (BMD) measurements between groups of subjects with and without vertebral fracture. To investigate whether differences in trabecular architecture may contribute to the presence or absence of fractures independent of the bone mass, fracture and nonfracture groups matched for age, gender, and BMD were assembled. Transiliac biopsies and corresponding lumbar spine BMD measurements from 31 women and 16 men with vertebral fracture were compared with those from 22 women and 11 men without fracture. Lumbar BMD (L1–4) was measured using a Hologic 2000 densitometer. The lumbar BMD was similar in women with and without fracture (0.63 g/cm 3 ± 0.10 SD and 0.71 g/cm 3 ± 0.17 SD, n.s.) and in men with and without fracture (0.72 g/cm 3 ± 0.12 SD and 0.76 g/cm 3 ± 0.17 SD, n.s.). Undecalcified iliac crest biopsy sections, 8 μm thick, were analyzed for remodeling variables and trabecular architecture using OsteoMeasure and TAS image analysis systems. No significant difference was found in either gender between fracture and nonfracture groups in percent bone volume (mean 10% in all groups), or in the wide range of remodeling and architectural variables measured, including the trabecular width, number, and separation, mean trabecular plate density and fractal dimension, as well as several indirect indices of connectivity including the node:terminus ratio, marrow star volume, and trabecular pattern factor. On the basis of this evidence it was concluded that there is no difference in the trabecular architecture between patients with crush fracture and controls when account is taken of bone mass. This suggests that microanatomical disruption is a predictable intrinsic feature of bone loss. However, there remains the possibility that the two-dimensional character of the structural deterioration measured indirectly is not sufficiently sensitive for the complex cancellous system. This is considered further in part II.