Bone-Forming and Antiresorptive Effects of Romosozumab in Postmenopausal Women With Osteoporosis: Bone Histomorphometry and Microcomputed Tomography Analysis After 2 and 12 Months of Treatment.

Sclerostin, a protein produced by osteocytes, inhibits bone formation. Administration of sclerostin antibody results in increased bone formation in multiple animal models. Romosozumab, a humanized sclerostin antibody, has a dual effect on bone, transiently increasing serum biochemical markers of bone formation and decreasing serum markers of bone resorption, leading to increased BMD and reduction in fracture risk in humans. We aimed to evaluate the effects of romosozumab on bone tissue. In a subset of 107 postmenopausal women with osteoporosis in the multicenter, international, randomized, double-blind, placebo-controlled Fracture Study in Postmenopausal Women with Osteoporosis (FRAME), transiliac bone biopsies were performed either after 2 (n = 34) or 12 (n = 73) months of treatment with 210 mg once monthly of romosozumab or placebo to evaluate histomorphometry and microcomputed tomography-based microarchitectural endpoints. After 2 months, compared with either baseline values assessed after a quadruple fluorochrome labeling or placebo, significant increases (P < 0.05 to P < 0.001) in dynamic parameters of formation (median MS/BS: romosozumab 1.51% and 5.64%; placebo 1.60% and 2.31% at baseline and month 2, respectively) were associated with a significant decrease compared with placebo in parameters of resorption in cancellous (median ES/BS: placebo 3.4%, romosozumab 1.8%; P = 0.022) and endocortical (median ES/BS: placebo 6.3%, romosozumab 1.6%; P = 0.003) bone. At 12 months, cancellous bone formation was significantly lower (P < 0.05 to P < 0.001) in romosozumab versus placebo and the lower values for resorption endpoints seen at month 2 persisted (P < 0.001), signaling a decrease in bone turnover (P = 0.006). No significant change was observed in periosteal and endocortical bone. This resulted in an increase in bone mass and trabecular thickness with improved trabecular connectivity, without significant modification of cortical porosity at month 12. In conclusion, romosozumab produced an early and transient increase in bone formation, but a persistent decrease in bone resorption. Antiresorptive action eventually resulted in decreased bone turnover. This effect resulted in significant increases in bone mass and improved microarchitecture. © 2019 American Society for Bone and Mineral Research.

Reduction of Cortical Bone Turnover and Erosion Depth After 2 and 3 Years of Denosumab: Iliac Bone Histomorphometry in the FREEDOM Trial.

Denosumab, a RANKL inhibitor, reduced the risk of vertebral, hip, and nonvertebral fractures in the Fracture REduction Evaluation of Denosumab in Osteoporosis every 6 Months (FREEDOM) trial of postmenopausal women with osteoporosis compared with placebo. Previous bone histomorphometric analysis in FREEDOM showed decreased bone resorption and turnover in cancellous bone after 2 and 3 years. The purpose of the present study was to evaluate the effects of denosumab compared with placebo in the cortical compartment from transiliac bone biopsies obtained during FREEDOM. A total of 112 specimens were evaluable for cortical histomorphometry, including 67 obtained at month 24 (37 placebo, 30 denosumab) and 45 at month 36 (25 placebo, 20 denosumab). Eroded surface, osteoclast surface, erosion depth, and wall thickness were measured on the endocortical surface. Cortical thickness and cortical porosity were also measured. Dynamic parameters of bone formation were assessed for endocortical, periosteal, and intracortical envelopes. Endocortical osteoclast surface, eroded surface, and mean and maximum erosion depth were significantly lower in the denosumab group versus placebo at months 24 and 36 (p < 0.0001 to p = 0.04). Endocortical wall thickness and intracortical measures (cortical porosity and cortical thickness) were not different between the two groups. Dynamic parameters were low with tetracycline labels in cortical bone observed in 13 (43%) and 10 (50%) of denosumab biopsies at months 24 and 36, respectively, reflecting a marked decrease in bone turnover. In conclusion, our data reveal the mechanism of action of denosumab on cortical bone: inhibition of osteoclastic resorption and reduced activation of new remodeling sites. In addition, reduced endocortical erosion depth with no change of wall thickness may contribute to increased bone strength by reducing the bone loss and fragility associated with deep resorption cavities and may likely contribute to the greater BMD gain with denosumab than with other antiresorptive agents. © 2018 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.

Spatial Distribution of Microcracks in Osteoarthritic Femoral Neck: Influence of Osteophytes on Microcrack Formation.

Osteophytes have been suggested to influence the bone mechanical properties. The aim of this study was to compare the microcrack density in osteophytes with that in the other parts of the osteoarthritic femoral neck (FN). The presence of microcracks was investigated in the ultra-distal FN and in the osteophytes in samples obtained during hip arthroplasty in 24 postmenopausal women aged 67 ± 10 years. Furthermore, the 3D microarchitecture and the collagen crosslinks contents were assessed by high-resolution peripheral quantitative computed tomography and high-performance liquid chromatography, respectively. Osteophytes were present in the 24 FN, mainly at the level of the inferior quadrant. Microcracks were present in all FN with an average of 2.8 per sample. All observed microcracks were linear. The microcrack density (Cr.N/BV; #/mm2) was significantly higher in cancellous than in cortical bone (p = 0.004), whereas the microcrack length (Cr.Le, µm) was significantly greater in cortical bone (p = 0.04). The collagen crosslinks ratio pyridinoline/deoxypyridinoline was significantly and negatively correlated with Cr.N/BV in the posterior (r' = - 0.68, p = 0.01) and inferior (r' = - 0.53, p = 0.05) quadrants. Microcracks were observed in seven osteophytes in seven patients. When microcracks were present in the osteophyte area, Cr.N/BV was also significantly higher in the whole FN and in the quadrant of the osteophyte compared to the cases without microcrack in the osteophyte (p < 0.03). In conclusion, in FN from hip osteoarthritis microcracks are present in all FNs but in only 23% of the osteophytes. The microcrack formation was greater and their progression was smaller in the cancellous bone than in the cortex. The spatial distribution of microcracks varied according to the proximity of the osteophyte, and suggests that osteophyte may influence microcrack formation related to changes in local bone quality.

Cortical Fractal Analysis and Collagen Crosslinks Content in Femoral Neck After Osteoporotic Fracture in Postmenopausal Women: Comparison with Osteoarthritis.

The femoral neck (FN) has been previously characterized by thinner cortices in osteoporotic fracture (HF) when compared to hip osteoarthritis (HOA). The purposes of this study were to complete the previous investigations on FNs from HF and HOA by analyzing the complexity of the cortical structure and to approach the intrinsic properties of cortical bone by assessing the collagen crosslink contents. FN samples were obtained during arthroplasty in 35 postmenopausal women (HF; n = 17; mean age 79 ± 2 years; HOA; n = 18; mean age 66 ± 2 years). The cortical fractal dimension (Ct.FD) and lacunarity (Ct.Lac) derived from high-resolution peripheral quantitative tomography (isotropic voxel size: 82 µm) images of FN by using Ctan software and Fraclac running in ImageJ were analyzed. The collagen crosslinks content [pyridinoline, deoxypyridinoline, pentosidine (PEN)] were assessed in cortical bone. Ct.FD was significantly lower (p < 0.0001) in HF than HOA reflecting a decreased complexity and was correlated to the age and BMD. In two sub-groups, BMD- and age-matched, respectively, Ct.FD remained significantly lower in HF than HOA (p < 0.001). Ct.Lac was not different between HF and HOA. PEN content was two times higher in HF than HOA (p < 0.0001) independently of age. In conclusion, FN with HF was characterized by a less complex cortical texture and higher PEN content than HOA. In addition to the decreased bone mass and BMD previously reported, these modifications contribute to the lower bone quality in HF than HOA in postmenopausal women.

Evaluation of cortical mandibular bone in patients with oral squamous cell carcinoma.

OBJECTIVES: The aim of the study was to evaluate the mandible cortical bone changes in patients with oral squamous cell carcinoma (OSCC). PATIENTS AND METHODS: Twenty patients who underwent some mandibular bone removal as part of the treatment of OSCC had bone samples collected in two parts: in the proximity of the tumor (BPT) and in the surgical margin (BEP). Cortical microarchitecture was analyzed trough micro-computed tomography, together with texture analysis, followed by microcrack evaluation in histological sections and gene expression of RANK, RANKL, OPG, and sclerostin by quantitative polymerase chain reaction. RESULTS: Bone surface was higher in BPT (0.005 ± 0.002 vs 0.004 ± 0.002, p = 0.01) compared with BEP. In BPT, the subset of patients without bone invasion presented higher anisotropy (0.83 ± 0.07) compared with the ones with bone invasion (0.70 ± 0.14) (p = 0.04). RANK, RANKL, OPG, and sclerostin were found to be downregulated in the majority of cases in both parts. There were significant correlations between the parameters of microarchitecture and gene expression analysis (p < 0.001 to p < 0.05), most of them related with OPG levels. CONCLUSION: The cortex in the mandible in the proximity of the tumor reveals more bone surface than the bone in the surgical margin, and the tumor invasion causes a decrease in anisotropy. RANK, RANKL, OPG, and sclerostin are downregulated in mandible, in both parts analyzed. Correlation tests revealed the association between cortical thickness, bone surface, anisotropy, porosity, bone mineral density, and OPG levels. CLINICAL RELEVANCE: The mandible cortical bone microarchitecture changes in the proximity of the squamous cell carcinoma lesion.

Are Biochemical Markers of Bone Turnover Representative of Bone Histomorphometry in 370 Postmenopausal Women?

CONTEXT: The levels of bone formation and resorption can be assessed at the tissue level by bone histomorphometry on transiliac bone biopsies. Systemic biochemical markers of bone turnover reflect the overall bone formation and resorption at the level of the entire skeleton but cannot discriminate the different skeletal compartments. OBJECTIVE: Our aim was to investigate the correlations between the serum biochemical markers of formation and resorption with histomorphometric parameters. DESIGN: We performed post hoc analysis of a previous clinical study. SETTING: Patients were selected from the general population. PATIENTS: A total of 371 untreated postmenopausal osteoporotic women aged 50 to 84 years with a lumbar T-score ≤ -2.5 SD or ≤ -1 SD with at least one osteoporotic fracture. INTERVENTIONS: Transiliac bone biopsies were obtained after a double tetracycline labeling, and blood samples were collected. MAIN OUTCOME MEASURES: The static and dynamic parameters of formation and bone resorption were measured by histomorphometry. Serum biochemical markers of formation (bone alkaline phosphatase [ALP]; procollagen type I N-terminal propeptide [PINP]) and resorption (C-terminal crosslinking telopeptide of collagen type 1 [sCTX]) were assessed. RESULTS: The mean values of biochemical markers were: bone ALP, 15.0 ± 5.2 ng/mL; PINP, 56.2 ± 21.9 µg/mL; and sCTX, 0.58 ± 0.26 ng/mL. Bone ALP and PINP were significantly correlated with both the static and dynamic parameters of formation (0.21 ≤ r' ≤ 0.36; 0.01 ≥ P ≥ .0001). sCTX was significantly correlated with all resorption parameters (0.18 ≤ r' ≤ 0.24; 0.02 ≥ P ≥ .0001). CONCLUSION: Bone turnover markers were significantly but modestly associated with bone turnover parameters measured in iliac cancellous bone. The iliac crest bone may not represent perfectly the whole bone turnover.

Bone histomorphometry of transiliac paired bone biopsies after 6 or 12 months of treatment with oral strontium ranelate in 387 osteoporotic women: randomized comparison to alendronate.

Preclinical studies indicate that strontium ranelate (SrRan) induces opposite effects on bone osteoblasts and osteoclasts, suggesting that SrRan may have a dual action on both formation and resorption. By contrast, alendronate (ALN) is a potent antiresorptive agent. In this multicenter, international, double-blind, controlled study conducted in 387 postmenopausal women with osteoporosis, transiliac bone biopsies were performed at baseline and after 6 or 12 months of treatment with either SrRan 2 g per day (n = 256) or alendronate 70 mg per week (n = 131). No deleterious effect on mineralization of SrRan or ALN was observed. In the intention-to-treat (ITT) population (268 patients with paired biopsy specimens), changes in static and dynamic bone formation parameters were always significantly higher with ALN compared with SrRan at month 6 (M6) and month 12 (M12). Static parameters of formation were maintained between baseline and the last value with SrRan, except for osteoblast surfaces, which decreased at M6. Significant decreases in the dynamic parameters of formation (mineralizing surface, bone formation rate, adjusted apposition rate, activation frequency) were noted at M6 and M12 in SrRan. Compared with ALN, the bone formation parameters at M6 and M12 were always significantly higher (p < 0.001) with SrRan. ALN, but not SrRan, decreased resorption parameters. Compared with the baseline paired biopsy specimens, wall thickness was significantly decreased at M6 but not at M12 and cancellous bone structure parameters (trabecular bone volume, trabecular thickness, trabecular number, number of nodes/tissue volume) were significantly decreased at M12 with SrRan; none of these changes were significantly different from ALN. In conclusion, this large controlled paired biopsy study over 1 year shows that the bone formation remains higher with a lower diminution of the bone remodeling with SrRan versus ALN. From these results, SrRan did not show a significant anabolic action on bone remodeling.

Microcrack frequency and bone remodeling in postmenopausal osteoporotic women on long-term bisphosphonates: a bone biopsy study.

UNLABELLED: We sought whether microdamage could rise in postmenopausal osteoporotic women on long-term bisphosphonates, as suggested by recent animal studies. We found few microcracks in iliac bone biopsies, despite a marked reduction in bone turnover. INTRODUCTION: Animal studies suggest that bisphosphonates (BPs) could increase microdamage frequency in a dose-dependent manner, caused by excessively suppressed bone turnover. However, there is limited data in humans receiving BP therapeutic doses for >3 yr. MATERIALS AND METHODS: We measured microcrack frequency and histomorphometry parameters on transiliac bone biopsies in 50 postmenopausal osteoporotic women (mean age = 68 yr) who had received BP therapy (3 on intravenous pamidronate, 37 on oral alendronate, and 10 on oral risedronate) for at least 3 yr (mean treatment duration = 6.5 yr). We compared these results with transiliac bone biopsies obtained from 12 cadavers. We used bulk staining with green calcein as a fluorochrome. The microcracks were quantified in three 100-microm-thick sections using optic microscopy and were confirmed by laser confocal microscopy. Microcrack frequency (number of microcracks/mm2 of bone tissue) was compared between treated women and controls using nonparametric tests. We also explored predictors of microcrack frequency, including age, duration of BP therapy, and activation frequency. RESULTS: Among treated women, cancellous bone microcrack frequency was low (mean, 0.13 microcracks/mm2) and did not differ significantly from that observed in controls (0.05 microcracks/mm2; p = 0.59). Of note, 54% of the treated women and 58% of the controls had no observable microcracks. There was no association between microcrack frequency and the duration of BP therapy (for microcracks/mm2 and duration, Spearman r = 0.04, p = 0.80) and between patients' ages and the number of microcracks (Spearman r = -0.09, p = 0.61). Although bone remodeling parameters were suppressed in treated women, we found no relationship between microcrack density and activation frequency (Spearman r = -0.003, p = 0.99). Also, microcrack frequency was not increased in women with prevalent vertebral fracture compared with those without fractures. CONCLUSIONS: Among postmenopausal osteoporotic women on long-term BPs, microcrack frequency in the iliac bone is low, despite a marked reduction of bone turnover.

Euler(strut.cavity), a new histomorphometric parameter of connectivity reflects bone strength and speed of sound in trabecular bone from human os calcis.

The amount of bone and the trabecular microarchitecture are two determinants of bone strength which can be quantified by bone histomorphometry. Among the parameters of bone microarchitecture, the Euler number developed in our laboratory (E( strut.cavity )) and trabecular bone pattern factor (TBPf) evaluate the connectivity and complexity independently of the bone quantity, and the speed of sound (SOS) measured by quantitative ultrasound (QUS) corroborates E( strut.cavity ). The aim of the present study was to validate E( strut.cavity ), TBPf, and SOS as parameters of bone microarchitecture and their contribution to bone strength. We examined 20 right os calcis taken after necropsy in 11 males and 9 females, aged 52-95 years. At the same anatomic location, we measured SOS and broadband ultrasound attenuation (BUA) using a Hologic Sahara device and bone mineral density (BMD) using a Hologic QDR 1000W. At this site a transcortical cylinder was cut for both apparent density measurement (Ap.Dens) and biomechanical tests (maximum compressive stress (sigma(max)) and Young's modulus (E)), and histomorphometry was performed with an automatic image analyzer (Visiolab, Explora Nova, France). E and sigma(max) were significantly correlated with the parameters of bone quantity, microarchitecture, and QUS. However, after adjustment for the bone quantity, E correlated only with E( strut.cavity ), TBPf, and SOS, and sigma(max) with BUA. In conclusion, the bone connectivity and complexity evaluated by E( strut.cavity ) and TBPf contribute to bone strength, independently of the bone quantity. The bone mechanical properties may be assessed, in os calcis, in the elastic domain by SOS and in the plastic domain by BUA.