An electron probe X-ray microanalytical study of bone mineral in osteogenesis imperfecta

A semiquantitative electron probe X-ray microan-alytical (XRMA) technique, in conjunction with transmission electron microscopy, was used to compare the calcium to phosphorus (Ca/P) molar ratios in calcium phosphate standards of known composition, in normal bone and in bone from patients with osteogenesis imperfecta (OI). Using a modified routine processing and resin embedding schedule, the measured Ca/P molar ratio of calcium phosphates standards of known composition were found to correlate well with the Ca/P molar ratio based on their respective chemical formulae. This technique was then used to compare the Ca/P molar ratio in normal human bone and in OI bone. The Ca/P ratio values for normal bone (Ca/P=1.631) correlated well with those for chemically prepared hydroxyapatite (Ca/P=1.602), but in bone from OI patients, the Ca/P molar ratio was significantly lower (Ca/P=1.488). This study has shown that there is a lower Ca/P molar ratio in OI bone compared with normal, matched bone. This suggests that the mineral deviates from the carbanoapatite usually found in bone. Isomorphous substitutions in the carbanoapatite lattice could account for this although this study has neither proved nor disproved this. The altered bone mineral is an-other factor that could contribute to the increased fracture rate observed in OI.     

Abnormal Mineral Composition of Osteogenesis Imperfecta Bone as Determined by Electron Probe X-ray Microanalysis on Conventional and Cryosections

Osteogenesis imperfecta (OI) is a genetic disorder of the connective tissue characterized by frequent bone fractures. The cause of bone fragility is still unknown even though substantial work on collagen has been done. We measured the calcium to phosphorus ratio (Ca/P) of bone mineral from 35 OI bone samples and 25 age- and site-matched control specimens, using electron probe X-ray microanalysis in the transmission electron microscope. Ultra-thin cryosections and conventionally prepared resin sections were used. Cryo-ultramicrotomy avoids any possible artifactual demineralization that may occur in conventional aqueous media. The Ca/P ratio obtained by these two methods was compared and there was no statistical difference between them. The results were differentiated according to the clinical types of OI for the first time. The Ca/P ratio of OI bone mineral was lower than normal in both resin and cryosections, and mirrored the severity of the disease. OI type II had the lowest ratio (Ca/P = 1.49) compared with normal age- and site-matched controls (Ca/P = 1.69). This abnormal mineral composition in OI type II could be a contributory factor to bone fragility in OI bone. Received: 1 June 1998 / Accepted: 23 December 1998     

Acellular Mineral Deposition in Collagen-Based Biomaterials Incubated in Cell Culture Media

Rapid developments in tissue engineering have renewed interest in biodegradable three-dimensional structures such as collagen-based biomaterials. Collagen matrices seeded in vitro with fibroblasts, osteoblasts, and chondrocytes can form tissues resembling skin, bone, and cartilage that could be used as functional substitutes for damaged tissues. Collagen is associated with both dystrophic calcification of collagenous implants and bone mineralization. We report here the calcification properties of collagen sponges incubated in cell-free media. Mineral deposited in sponges was identified by X-ray and electron diffraction, Fourier transform infrared spectroscopy, and the molar ratio of calcium:phosphorus (Ca:P) as a poorly crystalline apatite similar to bone. The degree of calcification increased with length of incubation and the Ca and P content of the media, with 10–15% Ca (dry weight) after 21 days' incubation in media containing 1.6–3 mM Ca and a Ca × P molar product of 2–3 mM², but only 2% Ca after incubation in medium with 1.33 mM Ca and a 1.7 mM² Ca × P molar product. Mineral deposition was completely inhibited in sponges that were washed extensively and initially contained less than 0.01% P. Readdition of phosphate in these sponges and subsequent freeze drying and sterilization restore their mineralization capacity, suggesting that collagen per se cannot initiate calcification and that the inorganic phosphate content associated with the collagen preparation process is in the solid state a potential nucleator. Addition of chondroitin 4-sulfate to the sponges partially or totally inhibited mineral deposition, even though 80–90% of the compound was released within 24 hours. These results indicate that acellular calcification of collagen-based biomaterials can occur under the culture conditions currently used in tissue engineering. Received: 30 October 1997 / Accepted: 30 September 1999     

Correlations Between Bone Mechanical Properties and Bone Composition Parameters in Mouse Models of Dominant and Recessive Osteogenesis Imperfecta and the Response to Anti‐TGF‐β Treatment

Osteogenesis imperfecta (OI) is a group of genetic disorders characterized by brittle bones that are prone to fracture. Although previous studies in animal models investigated the mechanical properties and material composition of OI bone, little work has been conducted to statistically correlate these parameters to identify key compositional contributors to the impaired bone mechanical behaviors in OI. Further, although increased TGF‐β signaling has been demonstrated as a contributing mechanism to the bone pathology in OI models, the relationship between mechanical properties and bone composition after anti‐TGF‐β treatment in OI has not been studied. Here, we performed follow‐up analyses of femurs collected in an earlier study from OI mice with and without anti‐TGF‐β treatment from both recessive (Crtap^‐/‐) and dominant (Col1a2^+/P.G610C) OI mouse models and WT mice. Mechanical properties were determined using three‐point bending tests and evaluated for statistical correlation with molecular composition in bone tissue assessed by Raman spectroscopy. Statistical regression analysis was conducted to determine significant compositional determinants of mechanical integrity. Interestingly, we found differences in the relationships between bone composition and mechanical properties and in the response to anti‐TGF‐β treatment. Femurs of both OI models exhibited increased brittleness, which was associated with reduced collagen content and carbonate substitution. In the Col1a2^+/P.G610C femurs, reduced hydroxyapatite crystallinity was also found to be associated with increased brittleness, and increased mineral‐to‐collagen ratio was correlated with increased ultimate strength, elastic modulus, and bone brittleness. In both models of OI, regression analysis demonstrated that collagen content was an important predictor of the increased brittleness. In summary, this work provides new insights into the relationships between bone composition and material properties in models of OI, identifies key bone compositional parameters that correlate with the impaired mechanical integrity of OI bone, and explores the effects of anti‐TGF‐β treatment on bone‐quality parameters in these models. © 2016 American Society for Bone and Mineral Research.     

An ultrastructural, microanalytical, and spectroscopic study of bone from a transgenic mouse with a COL1.A1 pro-alpha-1 mutation

A line of transgenic mice have been investigated that expressed moderate levels of an internally deleted human gene for the pro∝(I) chain of type I procollagen. These mice expressed the gene at approximately 50% that of the endogenous gene. The gene construct was modeled after a sporadic in-frame deletion of the human gene that produced a lethal variant of osteogenesis imperfecta by causing biosynthesis of shortened pro∝(I) chains. Periera et al. (1993) reported extensive fracturing in these mice with femurs that were shorter in length and bone that had decreased ash weight, mineral, and collagen content. These workers demonstrated an increased brittleness in bone using biomechanical measurements. The functional consequences of these mutant genes were examined in both transgenic and in normal littermate mice to determine if a valid model at the ultrastructural and analytical level had been produced for OI. X-ray microanalysis of bone mineral demonstrated a significantly lower calcium-to-phosphorus (Ca/P) molar ratio in transgenic mouse bone than in normal littermates; this was a feature of human OI bone. Fourier transform infrared spectroscopy confirmed that the mineral present was apatitic in nature despite the lower Ca/P molar ratio. Alizarin red skeletal staining showed the presence of multiple fracture calluses on the ribs and on the long bones of some of the transgenic mice, this was not seen on normal littermates. No light microscopic differences were observed between normal and transgenic mice; however, many ultrastructural correlates with human OI were observed in the transmission electron microscope. Anomalous fibrils associated with type I collagen, and an amorphous calcified material was observed lining the cartilage, extending beyond the lamina limitans in young transgenic mice.     

Formation chemistry of amorphous calcium phosphates prepared from carbonate containing solutions

Recent studies on synthetic amorphous calcium phosphates have indicated a regular chemical structure similar to a hydrated tricalcium phosphate with a Ca/P molar ratio of 1.5. The present study, which investigates the composition of amorphous calcium phosphates formed under varying conditions of pH and carbonate concentration, demonstrates that the structure of these amorphous precipitates is variable. The Ca/P ratio of the amorphous material increases with increasing pH, initial solution carbonate to phosphate molar ratio, initial solution CaxP mM² product, and initial solution Ca/P molar ratio. These changes in the solid are produced by changes in the percentage of phosphate present as acid phosphate, which decreases with increasing pH, and by changes in the carbonate concentration of the solid, which increases with increasing pH and with increasing initial solution CO₃/P molar ratio. It is suggested that biological amorphous calcium phosphates may be rich in both carbonate and acid phosphate and that the carbonate may represent the labile component of bone mineral carbonate. It is also suggested that a large fraction of bone acid phosphate may be associated with the amorphous calcium phosphate phase.     

Mechanical and mineral properties of osteogenesis imperfecta human bones at the tissue level

Osteogenesis imperfecta (OI) is a genetic disorder characterized by an increase in bone fragility on the macroscopic scale, but few data are available to describe the mechanisms involved on the tissue scale and the possible correlations between these scales. To better understand the effects of OI on the properties of human bone, we studied the mechanical and chemical properties of eight bone samples from children suffering from OI and compared them to the properties of three controls. High-resolution computed tomography, nanoindentation and Raman microspectroscopy were used to assess those properties. A higher tissue mineral density was found for OI bone (1.131 gHA/cm³ vs. 1.032 gHA/cm³, p = 0.032), along with a lower Young's modulus (17.6 GPa vs. 20.5 GPa, p = 0.024). Obviously, the mutation-induced collagen defects alter the collagen matrix, thereby affecting the mineralization. Raman spectroscopy showed that the mineral-to-matrix ratio was higher in the OI samples, while the crystallinity was lower, suggesting that the mineral crystals were smaller but more abundant in the case of OI. This change in crystal size, distribution and composition contributes to the observed decrease in mechanical strength.     

Pamidronate does not adversely affect bone intrinsic material properties in children with osteogenesis imperfecta

Cyclical intravenous pamidronate therapy increases bone mass in children with osteogenesis imperfecta (OI), but the effect on the intrinsic material properties of bone is unknown at present. Thus, a possible influence of pamidronate treatment on bone quality at the material level might negate the beneficial effects of the gain in bone mass and lead to bone fragility in the long term. In the present study, we used transiliac bone biopsy samples and assessed the intrinsic material properties of the bone tissue at the micron-level by combined backscattered electron imaging and nanoindentation. Paired iliac bone samples from 14 patients (age 3 to 17 years) with severe OI before and after 2.5 +/- 0.5 years (mean +/- SD) of pamidronate treatment as well as age-matched controls were examined. Bone histomorphometry was performed in all samples and confirmed an increase of bone mass in treated patients. Backscattered electron imaging was used to measure the weighted mean calcium content (Ca(Mean)), the most frequent calcium content (Ca(Peak)), the variation in mineralization (Ca(Width)) and the amount of lowly mineralized areas (Ca(Low)) that correspond to sites of primary mineralization. Nanoindentation was performed in a subgroup of 6 patients and 6 controls to determine hardness and elastic modulus. Compared to controls, untreated OI patients had a significantly higher degree of bone matrix mineralization (Ca(Peak) +7%, P < 0.001) and a strong reduction of Ca(Low) (-38%, P < 0.001) despite enhanced bone formation, as well as increased hardness (+21%, P < 0.01) and elastic modulus (+13%, P < 0.01). However, none of these parameters was significantly altered by the subsequent pamidronate treatment. This shows that OI bone is stiffer and more mineralized and that, despite the enhanced bone formation rate in these patients, areas of primary mineralization are hardly visible. We also conclude that pamidronate treatment in children with OI does not have an adverse effect on the intrinsic material properties of bone and, as a consequence, that a long-term administration of the drug might not increase brittleness and fragility of the bone matrix. The antifracture effectiveness of pamidronate treatment in OI, as shown in previous clinical studies, has to be explained by the increase of mainly cortical bone volume.     

Fourier Transform Infrared Imaging Spectroscopy (FT-IRIS) of Mineralization in Bisphosphonate-treated oim/oim Mice

Fourier transform infrared microscopy (FT-IRM) and imaging spectroscopy (FT-IRIS) are increasingly used to analyze the molecular components of mineralized tissues. A primary advantage of these techniques is the capability to simultaneously image the quantity and quality of multiple components in histological sections at 7 µm spatial resolution. In the current study, FT-IRM and FT-IRIS were used to characterize bone mineralization in a mouse model of osteogenesis imperfecta (OI) after treatment with the bisphosphonate alendronate (ALN). This application is currently relevant since recent studies have demonstrated great promise for the treatment of children with OI with bisphosphonates, but have not identified bisphosphonate-associated bone quality changes. Growing oim/oim mice, a model of moderate-to-severe OI, were treated with ALN (73 µg ALN/kg/day for 4 weeks followed by 26 µg/kg/day for 4 weeks) or saline from 6 to 14 weeks of age, and mineralization was evaluated in femoral cortical and metaphyseal bone. Infrared vibrations of the mineral (a carbonated apatite) and the matrix phases were monitored. The relative amounts of mineral and matrix present (min:matrix), the relative amount of carbonate present in the mineral (carb:min), and the crystallinity of the mineral phase were calculated. In untreated oim/oim bone, the min:matrix was greater and the crystallinity was reduced (indicative of less mature mineral) in the primary versus the secondary spongiosa, most likely due to the presence of calcified cartilage. With ALN treatment, the oim/oim mm:matrix increased in the secondary spongiosa, but the mineral crystallinity was not changed. In the cortical bone, no changes were evident with ALN treatment. These data demonstrate that in this mouse model, ALN treatment results in increased metaphyseal bone mineralization, but does not improve mineral maturity.     

Fkbp10 Deletion in Osteoblasts Leads to Qualitative Defects in Bone

Osteogenesis imperfecta (OI), also known as brittle bone disease, displays a spectrum of clinical severity from mild (OI type I) to severe early lethality (OI type II), with clinical features including low bone mass, fractures, and deformities. Mutations in the FK506 Binding Protein 10 (FKBP10), gene encoding the 65‐kDa protein FKBP65, cause a recessive form of OI and Bruck syndrome, the latter being characterized by joint contractures in addition to low bone mass. We previously showed that Fkbp10 expression is limited to bone, tendon, and ligaments in postnatal tissues. Furthermore, in both patients and Fkbp10 knockout mice, collagen telopeptide hydroxylysine crosslinking is dramatically reduced. To further characterize the bone specific contributions of Fkbp10, we conditionally ablated FKBP65 in Fkbp10^fl/fl mice (Mus musculus; C57BL/6) using the osteoblast‐specific Col1a1 2.3‐kb Cre recombinase. Using μCT, histomorphometry and quantitative backscattered electron imaging, we found minimal alterations in the quantity of bone and no differences in the degree of bone matrix mineralization in this model. However, mass spectroscopy (MS) of bone collagen demonstrated a decrease in mature, hydroxylysine‐aldehyde crosslinking. Furthermore, bone of mutant mice exhibits a reduction in mineral‐to‐matrix ratio and in crystal size as shown by Raman spectroscopy and small‐angle X‐ray scattering, respectively. Importantly, abnormalities in bone quality were associated with impaired bone biomechanical strength in mutant femurs compared with those of wild‐type littermates. Taken together, these data suggest that the altered collagen crosslinking through Fkbp10 ablation in osteoblasts primarily leads to a qualitative defect in the skeleton. © 2017 American Society for Bone and Mineral Research.     

Age-related changes in mineral of rat and bovine cortical bone

Summary The mineral of cortical bones has been studied in newborn, growing, and adult rats and in the calf and cow, using X-ray diffraction and infrared spectroscopy during the thermal decomposition of bones and by microassay of carbonate. The mineral of all the bone samples, regardless of species or age, was found to be a calcium-deficient apatite containing both CO₃ ²⁻ and HPO₄ ²⁻ ions in the crystal lattice. The crystal size, Ca/P molar ratio, and CO₃ ²⁻ ion content of cortical bone all increased with increasing age in both the rat and the bovine. The Ca/P ratio varied from 1.51 in newborn rats to 1.69 in adults but remained that of Ca-deficient apatite even though its value was close to that of stoichiometric hydroxyapatite (1.67). Both the carbonate ion and the hydrogenophosphate ion contents varied from one animal species to another and with age within a given species. Maturation was correlated with an increase in carbonate ion content, which replaced the HPO₄ ²⁻ ions. In contrast, the calcium ion number per unit formula did not vary during maturation. Cortical bone mineral, in both species, regardless of age, can therefore be represented by the following formula: Ca_8.3(PO₄)_4.3(CO₃)_x(HPO₄)_y(OH)_0.3; y decreased and x increased with increasing age, (x+y) being constant, equal to 1.7.     

Effects of combined androgen blockade on bone metabolism and density in men with locally advanced prostate cancer

Objective: To investigate whether combined androgen blockade (CAB) produces any adverse effects on bone metabolism and mineral density in patients with locally advanced prostate cancer.Materials and methods: The study group consisted of 17 stage T4 prostate cancer patients treated with CAB and had no evidence of bone metastasis on bone scintigraphy. The mean duration of CAB and final total prostate specific antigen (PSA) level at the time of study were found at 28.5 ± 15.9 (6–58) months and 0.39 ± 0.5 (0.1–2) ngml, respectively. Twenty age and socioeconomically matched benign prostate hyperplasia (BPH) patients were taken as the control group. Both groups were compared with regard to lumbar bone mineral density (LBD), femur bone mineral density (FBD) and serum parameters of bone metabolism namely calcium (Ca), phosphate (P), magnesium (Mg) and alkaline phosphatase (ALP). Bone mineral density was measured with dual energy x-ray absorptiometry.Results: The mean FBD, LBD and serum Ca, P, Mg and ALP measurement of the patients treated with CAB were 0.85 ± 0.1 g/cm², 1.16 ± 0.2 g/cm², 9.1 ± 0.3 mg/dl, 3.6 ± 0.6 mg/dl, 1.95 ± 0.14 mg/dl, 187.5 ± 61 mg/dl, respectively. No significant difference was found between patients subjected to CAB and the age matched controls in any of the studied parameters namely age, FBD, LBD, Ca, Mg and ALP except serum phosphate. Serum phosphate levels were significantly (p =0.001) higher in patients treated with CAB suggesting a minor effect of CAB on bone metabolism.Conclusion: No convincing evidence was found about the detrimental effect of CAB on bone mineral density and metabolism in a highly selected group of patients with advanced prostate cancer without bone metastases.     

Osteogenesis imperfecta type VI: a form of brittle bone disease with a mineralization defect.

Osteogenesis imperfecta (OI) is a heritable disease of bone in which the hallmark is bone fragility. Usually, the disorder is divided into four groups on clinical grounds. We previously described a group of patients initially classified with OI type IV who had a discrete phenotype including hyperplastic callus formation without evidence of mutations in type I collagen. We called that disease entity OI type V. In this study, we describe another group of 8 patients initially diagnosed with OI type IV who share unique, common characteristics. We propose to name this disorder "OI type VI." Fractures were first documented between 4 and 18 months of age. Patients with OI type VI sustained more frequent fractures than patients with OI type IV. Sclerae were white or faintly blue and dentinogenesis imperfecta was uniformly absent. All patients had vertebral compression fractures. No patients showed radiological signs of rickets. Lumbar spine areal bone mineral density (aBMD) was low and similar to age-matched patients with OI type IV. Serum alkaline phosphatase levels were elevated compared with age-matched patients with type IV OI (409 +/- 145 U/liter vs. 295 +/- 95 U/liter; p < 0.03 by t-test). Other biochemical parameters of bone and mineral metabolism were within the reference range. Mutation screening of the coding regions and exon/intron boundaries of both collagen type I genes did not reveal any mutations, and type I collagen protein analyses were normal. Qualitative histology of iliac crest bone biopsy specimens showed an absence of the birefringent pattern of normal lamellar bone under polarized light, often with a "fish-scale" pattern. Quantitative histomorphometry revealed thin cortices, hyperosteoidosis, and a prolonged mineralization lag time in the presence of a decreased mineral apposition rate. We conclude that type VI OI is a moderate to severe form of brittle bone disease with accumulation of osteoid due to a mineralization defect, in the absence of a disturbance of mineral metabolism. The underlying genetic defect remains to be elucidated.     

A morphological and ultrastructural study of bone in osteogenesis imperfecta

A morphological and electron microscopic study of bone from patients with osteogenesis imperfecta (OI) has been performed. Bone from OI patients from various anatomical sites has been compared with that from normal, age-, site-, and sex-matched controls. The morphology of OI bone appeared variable among patients and sites of bone examined. Immature woven bone and a poor lamellar pattern were the significant morphological features and demonstrated that OI could not be characterized on the basis of a single histological pattern. At the ultrastructural level, a number of previously unreported features were evident. Abnormal collagen fibers and an altered mineral composition were found in many OI patients, however, the panoramic heterogeneity between clinical types and indeed within a single clinical type made it difficult to classify OI in this manner. The presence of intermitochondrial inclusions containing calcium and phosphorus and the presence of a stromal calcification in the bone in some OI patients suggested an abnormal mineral formation. Qualitatively, no obvious difference in the number of osteoblasts or osteoclasts was observed. The morphology and ultrastructure of OI bone were good indicators of the disease and serve a role in assessing the progress of a patient through diagnosis and treatment. This report presents new ultrastructural findings in collagen and in mineral formation in OI compared with normal human bone.     

Changes in bone mineral in experimentally induced rickets in the rat: Electron microprobe and chemical studies

Summary The elemental composition of trabecular bone was compared for: (a) rats made rachitic on a low phosphorus, vitamin D-deficient diet; (b) rats fed the same diet but supplemented with vitamin D; (c) normal rats fed a standard laboratory diet with normal phosphorus and vitamin D levels. Quantitative energy dispersive X-ray microanalysis was performed on mineralized bone matrix at four sites: (1) clusters of mineral crystals in osteoid; (2) bone matrix adjacent to osteoid containing mineralization clusters; (3) peri-lacunar bone matrix; and (4) deep bone matrix distant from osteocytes. Estimations were also made of serum calcium, phosphorus, and 25-hydroxy-vitamin D, and of calcium, phosphorus, and hydroxyproline in whole bone. At bone sites 2, 3, and 4, the mineral content was greater in the normal group than in the other two groups. At each site, the mineral content of the rachitic bone matrix was greater than that from the vitamin D-treated group. A normal pattern of increasing mineral content with distance into the bone from a recently mineralized border was found in the normal and vitamin D-treated groups but was notably absent in the rachitic bones. Microprobe measurements of Ca:P molar ratios in hydroxyapatite standards and in normal rat bone were approximately 1.7. In both rachitic and vitamin D-treated bones, the Ca:P molar ratio was significantly higher than that in normal bones and correlated with serum Ca:P ratios. It is suggested that the increased Ca:P ratios in the rachitic and vitamin D-treated bones may be explained by an increased carbonate deposition.     

Calcium Kinetics in Children with Osteogenesis Imperfecta Type III and IV: Pre- and Post-Growth Hormone Therapy

Children with osteogenesis imperfecta (OI) type III and type IV were studied using a ⁴²Ca stable isotope technique. Serum dilution kinetics of ⁴²Ca were studied pre- and post-growth hormone (GH) treatment in 9 OI III (age range 5–9 years) and 8 OI IV patients (age range 5–12 years). Each subject was studied twice: at baseline and following GH therapy (range 1–1.5 years). Isotopic enrichments of ⁴²Ca were followed over 7 days using thermal ionization mass spectrometry. A binding site model, which describes reversible and irreversible binding of calcium (Ca) ions to postulated short- and long-term binding sites in bone, was used to analyze the kinetic data. In type III patients, GH treatment (1) increased the fraction of short-term binding sites, θ (0.777 ± 0.112 versus 0.877 ± 0.05, respectively; P= 0.034); (2) increased the apparent half-life of a Ca ion attached to the long-term binding site by 76% (P= 0.009); (3) although not statistically significant (P= 0.098), a trend toward an increased growth rate was observed with increasing change in θ (Δθ); (4) patients experienced a 75% increase in growth rate during the first 6 months of treatment. In type IV patients, GH treatment increased the apparent half-life of a Ca ion attached to the long-term binding site by 83% (P= 0.048), however, no trend toward an increased growth rate was observed with increasing Δθ in these patients. These significant changes in Ca binding to bone may influence growth in type III patients. Received: 10 September 1999 / Accepted: 29 February 2000     

The functional muscle–bone unit in patients with osteogenesis imperfecta type I

ContextOsteogenesis imperfecta (OI) type I is a heritable bone fragility disorder that is caused by mutations affecting collagen type I. We recently showed that patients with OI type I frequently have muscle weakness. As muscle force and bone mass are usually closely related, we hypothesized that muscle weakness in OI type I could contribute to increase bone mass deficit in the lower extremities.ObjectiveTo assess the muscle–bone relationship in the lower extremities of children and adolescents with OI type I.SettingThe study was carried out in the outpatients department of a pediatric orthopedic hospital.Patients and other participantsThirty children and adolescents with OI type I (20 females; mean age [SD]: 11.2 years [3.9]) were compared with 30 healthy age- and sex-matched controls (mean age [SD]: 11.1 years [4.5]).Main outcome measuresTibia bone mineral content (BMC; mg/mm) was measured by peripheral quantitative computed tomography to estimate bone strength at the 4% and 14% sites. Lower extremity peak force (kN) was measured by mechanography using the multiple two-legged hopping test.ResultsCompared with age- and sex-matched controls, patients with OI type I had 17% lower peak force (1.3 kN vs. 1.7 kN; p = 0.002) as well as a 22% lower BMC (128 mg/mm vs. 165 mg/mm; p < 0.001). Stepwise regression analysis showed that muscle force and tibia length were positively related to bone strength (r² = 0.90, p < 0.001) whereas there was no effect of the disease status (OI vs. control).ConclusionsThese results suggest that the muscle–bone relationship is similar between children and adolescents with OI type I and healthy age and sex-matched controls. It also suggests that muscle weakness may contribute to decreased bone strength in individuals with OI type I.     

K/DOQI guideline requirements for calcium, phosphate, calcium phosphate product, and parathyroid hormone control in dialysis patients: can we achieve them?

Background: Mineral metabolism has emerged as an important predictor of morbidity and mortality in dialysis patients. Kidney Disease Outcomes Quality Initiative (K/DOQI) clinical practice guidelines for bone metabolism and disease in chronic kidney disease (CKD) recommend that, in Stage 5 CKD, the target levels for calcium (Ca) (corrected for serum albumin), phosphate (P), calcium × phosphate (Ca × P) product and parathyroid hormone (PTH) levels should be maintained at 8.4–9.5 mg/dl, 3.5–5.5 mg/dl, < 55 mg²/dl² and 150–300 pg/ml, respectively. Objectives: To evaluate our ability to achieve K/DOQI guidelines for bone metabolism and disease targets in our patients and to compare them between patients on hemodialysis (HD) and peritoneal dialysis (PD) and also with those reported in the literature. Methods: We reviewed bone metabolism laboratory parameters in 57 HD patients and 69 PD patients, who had been on dialysis for more than 9 months. Results: The percentage of patients whose serum Ca, P, Ca × P product and PTH were within K/DOQI recommended target ranges were 46%, 53%, 77% and 28% in HD patients and 52%, 65%, 77% and 23% in PD patients, respectively. There were no significant differences between HD and PD patients in the percentage of all parameters that were within K/DOQI recommended target ranges. The percentage of our HD patients who had Ca, P, and PTH levels within recommended target range was similar to those in previous reports. Conclusion: In our unit, the management of bone and mineral metabolism in HD and PD patients is still far short of meeting K/DOQI guidelines. These findings appear similar in HD and PD patients. Our findings resemble those reported in the literature.     

Effect of the Proportion of Organic Material in Bone on Thermal Decomposition of Bone Mineral: An Investigation of a Variety of Bones from Different Species Using Thermogravimetric Analysis coupled to Mass Spectrometry,High-Temperature X-ray Diffraction,and Fourier Transform Infrared Spectroscopy

Thermogravimetric analysis linked to mass spectrometry (TGA-MS) shows changes in mass and identifies gases evolved when a material is heated. Heating to 600 degrees C enabled samples of bone to be classified as having a high (cod clythrum, deer antler, and whale periotic fin bone) or a low (porpoise ear bone, whale tympanic bulla, and whale ear bone) proportion of organic material. At higher temperatures, the mineral phase of the bone decomposed. High temperature X-ray diffraction (HTXRD) showed that the main solids produced by decomposition of mineral (in air or argon at 800 degrees C to 1000 degrees C) were beta-tricalcium phosphate (TCP) and hydroxyapatite (HAP), in deer antler, and CaO and HAP, in whale tympanic bulla. In carbon dioxide, the decomposition was retarded, indicating that the changes observed in air and argon were a result of the loss of carbonate ions from the mineral. Fourier transform infrared (FTIR) spectroscopy of bones heated to different temperatures, showed that loss of carbon dioxide (as a result of decomposition of carbonate ions) was accompanied by the appearance of hydroxide ions. These results can be explained if the structure of bone mineral is represented by [Formula: see text] where V(Ca) and V(OH) correspond to vacancies on the calcium and hydroxide sites, respectively, and 2-x-y = 0.4. This general formula is consistent in describing both mature bone mineral (i.e., whale bone), with a high Ca/P molar ratio, lower HPO4(2-) content, and higher CO3(2-) content, and immature bone mineral (i.e., deer antler), with a low Ca/P ratio, higher HPO4(2-), and lower CO3(2-) content.     

The effect of calcium supplement given with a mixture of calcium carbonate and calcium citrate on the mandibular alveolar bone of pubertal rats

To determine whether the mixture of calcium carbonate and calcium citrate, an oral calcium supplement made from sea shell that is called UNICAL, had any beneficial effect on bone debilitation, we examined the mandibular alveolar bone of pubertal Wistar male rats by bone mineral mass, Ca/P ratio microanalysis, and scanning electron microscopy. (1) Bone mineral mass of UNICAL-fed rats in the low-calcium experiment group was not significantly different than the control group, although its value was significantly higher than in pair-fed standard diet rats. However, although the bone mineral mass of UNICAL diet rats in the calcium-deficient experiment group was significantly higher than in pair-fed standard diet rats, it was significantly lower than in the control group. (2) All Ca : P ratio values in experiment groups were significantly lower than that in control group. Ca : P ratio values of UNICAL diet rats were significantly higher than those of pair-fed standard diet rats in experiment groups. Separately, Ca : P ratio was not significantly different between UNICAL diet rats of the calcium-deficient experiment group and standard diet rats of the low-calcium experiment group. (3) On scanning electron microscope observation, UNICAL diet animals were observed to have more sufficient calcareous microdepositions in bone remodeling areas, which was thought to be one of the morphological indications of bone formation, reflecting active calcium utilization in bone metabolism, than pair-fed standard diet animals. These results suggested that the mixture of calcium carbonate and calcium citrate had a positive effect on bone debilitation to a certain extent in growth-period rats. Received: Nov. 25, 1997 / Accepted: Jan. 29, 1998