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.

Evaluation of Romosozumab's Effects on Bone Marrow Adiposity in Postmenopausal Osteoporotic Women: Results from the FRAME Bone Biopsy Sub-Study.

Romosozumab, a humanized monoclonal antibody that binds and inhibits sclerostin produces a marked increase in bone formation with a concomitant decreased bone resorption. This transient rise in bone formation in the first two months of treatment is mainly due to an increased modeling-based bone formation. This requires the recruitment and differentiation of osteoblasts, one possibility being a preferential switch in commitment of precursors to osteoblasts over adipocytes. The purpose of this study was to analyze the marrow adiposity in transiliac bone biopsies at months 2 or 12 from the FRAME biopsy sub-study in patients receiving romosozumab or placebo. The total adipocyte area, number and density were measured on the total cancellous bone area. The size and shape at the individual adipocyte level were assessed including the mean adipocyte area, perimeter, min and max diameters and aspect ratio. No significant difference in total adipocyte area, number or density between placebo and romosozumab groups was observed at months 2 and 12, and no difference was observed between 2 and 12 months. After 2 or 12 months, romosozumab did not modify the size or shape of the adipocytes. No relationship between the adipocyte parameters and the dynamic parameters of bone formation could be evidenced. In conclusion, based on the analysis of a small number of biopsies, no effect of romosozumab on bone marrow adiposity of iliac crest was identified after 2 and 12 months suggesting that the modeling-based formation observed at month 2 was not due to a preferential commitment of the precursor to osteoblast over adipocyte cell lines but may result from a reactivation of bone lining cells and from a progenitor pool independent of the marrow adipocyte population.

Osteoporosis is characterized by bone loss resulting from an imbalance between the bone resorption and the bone formation in favor of the resorption. Romosozumab, a new medication to treat osteoporosis, has been shown to induce an early transient increase in bone formation that requires the differentiation of new bone forming cells called osteoblasts. Osteoblasts and fat-containing cells known as adipocytes present in the bone marrow originate from a common precursor cell. Thus, a preferential switch of this precursor to osteoblast over adipocyte is thought to be a possible cause for the increase in bone formation. The purpose of this study was to analyze the bone marrow adipocytes on bone biopsies from the pelvis in osteoporotic patients treated with romosozumab in order to evaluate that possibility. After treatment, the proportion of adipocytes, their size and shape, did not change when compared to untreated patients. In conclusion, no effect of romosozumab on bone marrow adipocytes was identified suggesting that the increased bone formation induced by romosozumab was not due to a preferential differentiation of precursor cells to osteoblasts over adipocytes.

Reconstruction of remodeling units reveals positive effects after 2 and 12 months of romosozumab treatment.

Romosozumab treatment results in a transient early increase in bone formation and sustained decrease in bone resorption. Histomorphometric analyses revealed that the primary bone-forming effect of romosozumab is a transient early stimulation of modeling-based bone formation on cancellous and endocortical surfaces. Furthermore, preclinical studies have demonstrated that romosozumab may affect changes in the remodeling unit, resulting in positive bone balance. To further investigate the effects of romosozumab on bone balance, mo 12 (M12) and mo 2 (M2) (to analyze early effects) unpaired bone biopsies from the FRAME clinical trial were analyzed using remodeling site reconstruction to assess whether positive changes in bone balance on cancellous/endocortical surfaces may contribute to the progressive improvement in bone mass/structure and reduced fracture risk in osteoporotic women at high fracture risk. At M12, bone balance was higher with romosozumab vs placebo on cancellous (+6.1 vs +1.5 µm; P = .012) and endocortical (+5.2 vs -1.7 µm; P = .02) surfaces; higher bone balance was due to lower final erosion depth (40.7 vs 43.7 µm; P = .05) on cancellous surfaces and higher completed wall thickness (50.8 vs 47.5 µm; P = .037) on endocortical surfaces. At M2, the final erosion depth was lower on the endocortical surfaces (42.7 vs 50.7 µm; P = .021) and was slightly lower on the cancellous surfaces (38.5 vs 44.6 µm; P = .11) with romosozumab vs placebo. Sector analysis of early endocortical formative sites revealed higher osteoid thickness (29.9 vs 19.2 µm; P = .005) and mineralized wall thickness (18.3 vs 11.9 µm; P = .004) with romosozumab vs placebo. These evolving bone packets may reflect the early stimulation of bone formation that contributes to the increase in completed wall thickness at M12. These data suggest that romosozumab induces a positive bone balance due to its effects on bone resorption and formation at the level of the remodeling unit, contributing to the positive effects on bone mass, structure, and fracture risk.

Romosozumab treatment has a dual effect on bone, adding new bone and reducing bone loss. In the FRAME clinical trial, romosozumab increased the bone mass and strength and reduced fracture risk in postmenopausal women with osteoporosis. Addition of new bone occurs early in treatment and rapidly on cancellous and endocortical bone surfaces where bone resorption is not ongoing. However, it remains unclear if romosozumab affects bone loss or gain in areas where bone resorption is ongoing (remodeling units), contributing to a further positive bone balance. Here, we examined whether changes at the remodeling unit occur early (2 mo) and/or late (12 mo) in treatment by using bone biopsies from patients treated with romosozumab or placebo in FRAME. At M2, a combination of lower bone resorption and higher bone gain on endocortical surfaces resulted in a positive bone balance with romosozumab vs placebo. At M12, the bone balance was positive with romosozumab vs placebo due to lower bone resorption on cancellous surfaces and greater bone gain on endocortical surfaces. This demonstrates that romosozumab induces a positive bone balance at remodeling units early in treatment, leading to overall gains observed later, contributing to the positive effects of romosozumab on bone mass and structure.

Interest of Bone Histomorphometry in Bone Pathophysiology Investigation: Foundation, Present, and Future.

Despite the development of non-invasive methods, bone histomorphometry remains the only method to analyze bone at the tissue and cell levels. Quantitative analysis of transiliac bone sections requires strict methodologic conditions but since its foundation more 60 years ago, this methodology has progressed. Our purpose was to review the evolution of bone histomorphometry over the years and its contribution to the knowledge of bone tissue metabolism under normal and pathological conditions and the understanding of the action mechanisms of therapeutic drugs in humans. The two main applications of bone histomorphometry are the diagnosis of bone diseases and research. It is warranted for the diagnosis of mineralization defects as in osteomalacia, of other causes of osteoporosis as bone mastocytosis, or the classification of renal osteodystrophy. Bone biopsies are required in clinical trials to evaluate the safety and mechanism of action of new therapeutic agents and were applied to anti-osteoporotic agents such as bisphosphonates and denosumab, an anti-RANKL, which induces a marked reduction of the bone turnover with a consequent elongation of the mineralization period. In contrast, an increased bone turnover with an extension of the formation site is observed with teriparatide. Romosozumab, an anti-sclerostin, has a dual effect with an early increased formation and reduced resorption. Bone histomorphometric studies allow us to understand the mechanism of coupling between formation and resorption and to evaluate the respective role of bone modeling and remodeling. The adaptation of new image analysis techniques will help bone biopsy analysis in the future.

Modeling-Based Bone Formation After 2 Months of Romosozumab Treatment: Results From the FRAME Clinical Trial.

The bone-forming agent romosozumab is a monoclonal antibody that inhibits sclerostin, leading to increased bone formation and decreased resorption. The highest levels of bone formation markers in human patients are observed in the first 2 months of treatment. Histomorphometric analysis of bone biopsies from the phase 3 FRAME trial (NCT01575834) showed an early significant increase in bone formation with concomitant decreased resorption. Preclinical studies demonstrated that most new bone formation after romosozumab treatment was modeling-based bone formation (MBBF). Here we analyzed bone biopsies from FRAME to assess the effect of 2 months of romosozumab versus placebo on the surface extent of MBBF and remodeling-based bone formation (RBBF). In FRAME, postmenopausal women aged ≥55 years with osteoporosis were randomized 1:1 to 210 mg romosozumab or placebo sc every month for 12 months, followed by 60 mg denosumab sc every 6 months for 12 months. Participants in the bone biopsy substudy received quadruple tetracycline labeling and underwent transiliac biopsies at month 2. A total of 29 biopsies were suitable for histomorphometry. Using fluorescence microscopy, bone formation at cancellous, endocortical, and periosteal envelopes was classified based on the appearance of underlying cement lines as modeling (smooth) or remodeling (scalloped). Data were compared using the Wilcoxon rank-sum test, without multiplicity adjustment. After 2 months, the median percentage of MBBF referent to the total bone surface was significantly increased with romosozumab versus placebo on cancellous (18.0% versus 3.8%; p = 0.005) and endocortical (36.7% versus 3.0%; p = 0.001), but not on periosteal (5.0% versus 2.0%; p = 0.37) surfaces, with no significant difference in the surface extent of RBBF on all three bone surfaces. These data show that stimulation of bone formation in the first 2 months of romosozumab treatment in postmenopausal women with osteoporosis is predominately due to increased MBBF on endocortical and cancellous surfaces. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Alendronate prolongs the reversal-resorption phase in human cortical bone remodeling.

Despite their ability to reduce fracture-risk and increase Bone Mineral Density (BMD) in osteoporotic women, bisphosphonates are reported to reduce formation of new bone. Reduced bone formation has been suggested to lead to accumulation of microfractures and contribute to rare side effects in cortical bone such as atypical femur fractures. However, most studies are limited to trabecular bone. In this study, the cortical bone remodeling in human iliac bone specimens of 65 non-treated and 24 alendronate-treated osteoporotic women was investigated using a new histomorphometric classification of intracortical pores. The study showed that only 12.4 ± 11% of the cortical pore area reflected quiescent pores/osteons in alendronate-treated patients versus 8.5 ± 5% in placebo, highlighting that new cortical remodeling events remain to be activated. The percent and size of eroded pores (events in resorption-reversal phase) remained unchanged, but their contribution to total pore area was 1.4-fold higher in alendronate versus placebo treated patients (66 ± 22% vs 48 ± 22%, p < 0.001). On the other hand, the mixed eroded-formative pores (events with mixed resorption-reversal-formation phases) was 2-fold lower in alendronate versus placebo treated patients (19 ± 14% vs 39 ± 23% of total pore area, p < 0.001), and formative pores (event in formation phase) was 2.2-fold lower in alendronate versus placebo treated patients (2.1 ± 2.4% vs 4.6 ± 3.6%, p < 0.01), and their contribution to total pore area was 2.4-fold lower (1.3 ± 2.1% vs 3.1 ± 4.4%, p < 0.05). Importantly, these differences between alendronate and placebo treated patients were significant in patients after 3 years of treatment, not after 2 years of treatment. Collectively, the results support that cortical remodeling events activated during alendronate treatment has a prolonged reversal-resorption phase with a delayed transition to formation, becoming increasingly evident after 3-years of treatment. A potential contributor to atypical femur fractures associated with long-term bisphosphonate treatment.

Bisphosphonates impair the onset of bone formation at remodeling sites.

Bisphosphonates are widely used anti-osteoporotic drugs targeting osteoclasts. They strongly inhibit bone resorption, but also strongly reduce bone formation. This reduced formation is commonly ascribed to the mechanism maintaining the resorption/formation balance during remodeling. The present study provides evidence for an additional mechanism where bisphosphonates actually impair the onset of bone formation after resorption. The evidence is based on morphometric parameters recently developed to assess the activities reversing resorption to formation. Herein, we compare these parameters in cancellous bone of alendronate- and placebo-treated postmenopausal osteoporotic patients. Alendronate increases the prevalence of eroded surfaces characterized by reversal cells/osteoprogenitors at low cell density and remote from active bone surfaces. This indicates deficient cell expansion on eroded surfaces - an event that is indispensable to start formation. Furthermore, alendronate decreases the coverage of these eroded surfaces by remodeling compartment canopies, a putative source of reversal cells/osteoprogenitors. Finally, alendronate strongly decreases the activation frequency of bone formation, and decreases more the formative compared to the eroded surfaces. All these parameters correlate with each other. These observations lead to a model where bisphosphonates hamper the osteoprogenitor recruitment required to initiate bone formation. This effect results in a larger eroded surface, thereby explaining the well-known paradox that bisphosphonates strongly inhibit bone resorption without strongly decreasing eroded surfaces. The possible mechanism for hampered osteoprogenitor recruitment is discussed: bisphosphonates may decrease the release of osteogenic factors by the osteoclasts, and/or bisphosphonates released by osteoclasts may act directly on neighboring osteoprogenitor cells as reported in preclinical studies.

Duration-Dependent Increase of Human Bone Matrix Mineralization in Long-Term Bisphosphonate Users with Atypical Femur Fracture.

Bisphosphonates (BPs) are the most widely used drugs for the treatment of osteoporosis but prolonged use of BPs might increase the risk of atypical femur fracture (AFF). There are only a few studies that address the bone material quality in patients on long-term BP treatment with or without AFFs. We analyzed 52 trans-iliac bone biopsies from patients on long-term BP therapy with (n = 26) and without (n = 26) AFF. At the microscopic level, the degree of mineralization of bone (DMB) was assessed on whole bone by X-ray digitized microradiography while microhardness by Vickers microindentation, and bone matrix characteristics by Fourier transform infrared microspectroscopy (FTIRM) (mineral/organic ratio, mineral maturity and crystallinity, and collagen maturity) were measured at random focal areas. The AFF patients were treated longer than non-AFF patients (9.7 ± 3.3 years versus 7.9 ± 2.7 years). As expected, bone remodeling was low in both groups, without difference between them. The AFF group had significantly higher DMB in cortical bone (+2.9%, p = .001), which remained so after adjusting for treatment duration (p = .007), and showed a trend in cancellous bone (+1.6%, p = .05). Consistent with higher DMB, heterogeneity index (HI) was lower in the AFF than in the non-AFF group, illustrating lower heterogeneity of mineralization in the AFF group. A significant positive correlation between the duration of treatment and DMB in cortical bone was found in AFF, and not in the non-AFF group. Microhardness and bone matrix characteristics were similar between groups. We conclude that the AFF group had a duration-dependent increase in DMB leading to a significantly higher DMB than the non-AFF. Because BPs have high affinity to bone mineral and lining the walls of the osteocyte lacunae, the accumulation of matrix-bound BPs in AFF could lead to inhibition of the osteocyte cytoskeleton blunting their response to mechanical strains, a hypothesis to be further investigated. © 2021 American Society for Bone and Mineral Research (ASBMR).

Bone Phenotyping Approaches in Human, Mice and Zebrafish - Expert Overview of the EU Cost Action GEMSTONE ("GEnomics of MusculoSkeletal traits TranslatiOnal NEtwork").

A synoptic overview of scientific methods applied in bone and associated research fields across species has yet to be published. Experts from the EU Cost Action GEMSTONE ("GEnomics of MusculoSkeletal Traits translational Network") Working Group 2 present an overview of the routine techniques as well as clinical and research approaches employed to characterize bone phenotypes in humans and selected animal models (mice and zebrafish) of health and disease. The goal is consolidation of knowledge and a map for future research. This expert paper provides a comprehensive overview of state-of-the-art technologies to investigate bone properties in humans and animals - including their strengths and weaknesses. New research methodologies are outlined and future strategies are discussed to combine phenotypic with rapidly developing -omics data in order to advance musculoskeletal research and move towards "personalised medicine".

Impact microindentation measurements correlate with cortical bone material properties measured by Fourier transform infrared imaging in humans.

Bone Material Strength index (BMSi) measured by Impact Microindentation is generally lower in subjects with fragility fractures independently of BMD values. We recently reported that in humans, BMSi values are strongly associated with material properties of subperiosteal mineralized bone surface (local mineral content, nanoporosity, pyridinoline content). In the present study we investigated the relationship of BMSi with material properties of the whole bone cortex, by analyzing thin sections of iliac crest biopsies (N = 12) from patients with different skeletal disorders and a wide range of BMD with or without fractures, by Fourier transform infrared imaging (FTIRI). The calculated parameters were: i) mineral and organic matrix content and their ratio (MM), ii) mineral maturity/crystallinity (MMC) and iii) the ratio of pyridinoline (Pyd) and divalent collagen cross-links (XLR). Results were expressed as images, which were converted to histogram distributions. For each histogram the characteristics recorded were: mean value, mode (most often occurring value), skewness, and kurtosis and their association with BMSi values was examined by correlation analysis. BMSi values were significantly correlated only with MM mean and mode values (r = 0.736, p = 0.0063, and r = 0.855, p = 0.0004, respectively), and with XLR mode values (r = -0.632, p = 0.0274). The results of the present study demonstrate that BMSi values are strongly associated with MM, a metric that corrects the mineral content for the organic matrix content, and may also depend on organic matrix quality. These and our previous observations strongly suggest that BMSi assesses material properties of cortical bone.

Impact microindentation assesses subperiosteal bone material properties in humans.

Impact microindentation (IMI) is a Reference Point Indentation technique measuring tissue-level properties of cortical bone in humans in vivo. The nature, however, of the properties that can affect bone strength is incompletely understood. In the present study we examined bone material properties in transiliac bone biopsies obtained concurrently with measurements of Bone Material Strength index (BMSi) by IMI in 12 patients with different skeletal disorders and a wide range of BMD, with or without fractures (8 males, 4 females, mean age 48±12.2 (SD) years, range 15-60 years). IMI was performed in the mid-shaft of the right tibia with a hand-held microindenter (OsteoProbe). Cancellous and cortical bone mineralization density distributions (BMDD) were measured in the entire biopsy bone area by quantitative backscattered electron imaging. Raman measurements were obtained right at the outer edge of the cortex, and 5, 50, 100, 500µm inwards. The calculated parameters were: i) Mineral and organic matrix content as well as the mineral / matrix ratio. ii) Nanoporosity. iii) Glycosaminoglycan content. iv) Pyridinoline content. v) Maturity/crystallinity of the apatite crystallites. There was no relationship between BMSi values with any measurement of mineral content of whole bone tissue (BMD, BMDD) or maturity/crystallinity of bone mineral. On the other hand, a positive correlation between BMSi and local mineral content, and an inverse correlation between BMSi and nanoporosity at the mineralized subperiosteal edge of the sample and at 5µm inwards was found. A positive correlation was also observed between BMSi and pyridinoline content at the same locations. These results indicate that local mineral content, nanoporosity and pyridinoline content at the subperiosteal site in the transiliac bone biopsy are linked to the BMSi values measured in the tibia. As both high porosity at the nano level and low pyridinoline content of the bone matrix can negatively impact bone strength, our findings suggest that BMSi most likely assesses subperiosteal bone material properties.

Homozygous Loss-of-Function Mutations in CCDC134 Are Responsible for a Severe Form of Osteogenesis Imperfecta.

Osteogenesis imperfecta (OI) is a primary bone fragility disorder with an estimated prevalence of 1 in 15,000 births. The majority of OI cases are inherited in an autosomal-dominant manner, while 5% to 10% have recessive or X-linked inheritance. Up to now, approximately 5% of OI cases remain without mutation demonstrated, supporting the involvement of other genes in the disease spectrum. By whole-exome sequencing, we identified a homozygous variant (c.2T>C) in CCDC134 gene in three patients from two unrelated families with severe bone fragility that did not respond to bisphosphonate treatment, short stature, and gracile long bones with pseudarthroses but no dentinogenesis imperfecta. CCDC134 encodes a secreted protein widely expressed and implicated in the regulation of some mitogen-activated protein kinases (MAPK) signaling pathway. Western blot and immunofluorescence analyses confirmed the absence of CCDC134 protein in patient cells compared with controls. Furthermore, we demonstrated that CCDC134 mutations are associated with increased Erk1/2 phosphorylation, decreased OPN mRNA and COL1A1 expression and reduced mineralization in patient osteoblasts compared with controls. These data support that CCDC134 is a new gene involved in severe progressive deforming recessive osteogenesis imperfecta (type III). © 2020 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.

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.

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.

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.

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.

Bisphosphonate-Related Osteonecrosis of the Jaws and Its Array of Manifestations.

PURPOSE: Bisphosphonate (BP) therapy in the treatment of bone diseases and malignancy may induce a major side effect known as bisphosphonate-related osteonecrosis of the jaws (BRONJ). A particular view of this condition is reported in this case series investigating eight patients. The aim of the study was to evaluate the BRONJ lesions concerning their aspects and progression. Also, identify if it is possible to predict the degree of severity in these cases. METHODS: Patients were evaluated by their condition and systemic health. The lesions were evaluated in clinical and radiographic aspects. The patients were followed-up for 2 years. RESULTS: The patients presented with specific peculiarities, and the BRONJ lesions varied in several characteristics. The BRONJ lesions ranged from simple to severe conditions, and the complicated cases presented with major pain, swelling, secondary infection and an extensive necrotic area, classified with high grade of severity. CONCLUSIONS: The patients presented here confirm the existence of a relation between multiple features and BRONJ and to understand the whole process of aggravation, all systemic and local information have to be taken into account, together with all data related to the BP utilized. Regardless of the low incidence of this side effect in relation to osteoporosis treatment, in some cases, the BRONJ may become a severe condition and compromise the patient's quality of life.