Biomedical subjects
Masako Ito
Publications and source records attributed to Masako Ito.
Effects of risedronate on trabecular microstructure and biomechanical properties in ovariectomized rat tibia.
We determined the effect of risedronate on the trabecular microstructure of ovariectomized rat tibiae, using micro-computed tomography, in order to investigate how changes in microstructure contribute to biomechanical properties. Fifty 18-week-old rats underwent sham operation (n=10) or ovariectomy (OVX) (n=40). The OVX rats were further divided into four groups (n=10 for each group) and treated with risedronate at doses of 0, 0.1, 0.5 or 2.5 mg/kg for 9 months. OVX caused deterioration of three-dimensional trabecular microstructure, notably structure model index (SMI) and connectivity density, while treatment of OVX rats with risedronate at 0.5 and 2.5 mg/kg improved those deleterious microstructural changes. Biomechanical property, as assessed by finite element analysis (FEA), correlated significantly with trabecular bone volume fraction (BV/TV), and the correlation further increased substantially when microstructural parameters were added, especially SMI and connectivity density, with risedronate therapy. Thus, it is suggested that, in addition to increasing bone mass, risedronate improves biomechanical property by maintaining a plate-like structure as well as connectivity of trabeculae.
Assessment of bone quality using micro-computed tomography (micro-CT) and synchrotron micro-CT.
The latest micro-computed tomography (micro-CT) can provide ultrahigh-resolution images with resolution of less than 10 microm. Geometric three-dimensional (3-D) parameters, including the orientation, shape, and connectivity of trabeculae, are particularly helpful in understanding complex 3-D structure. Micro-CT is helpful for studying bone changes in various pathophysiological states and assessing changes in microarchitecture after treatment with antiosteoporotic agents. Trabecular microarchitecture is strongly related to bone strength, and 3-D micro-CT data can be used to assess bone biomechanical properties with the help of finite-element analysis. High photon flux from synchrotron X-ray sources reveals precise bone surface structure, and the monochromaticity of the beam is suitable for performing accurate density measurements. The preliminary results of an in vivo study of microarchitecture are also shown. Human vertebral microstructure can be revealed using multidetector row CT at a resolution of 200 x 200 x 300 microm. Analysis using high-resolution CT microstructure was found to be more useful in identifying subjects at high risk of fracture than clinical bone density measurements using dual X-ray absorptiometry.
Ataxia telangiectasia mutated (Atm) knockout mice as a model of osteopenia due to impaired bone formation.
ATM is a member of the PI-3 kinase protein family, encoded by the gene, ATM, responsible for ataxia telangiectasia (AT). AT is recognized as a genomic instability syndrome, sharing accelerated senescence symptoms in human and mouse. Here, we present evidence that the bone phenotype of Atm knockout (AtmKO) mice is similar to that observed in disuse and/or aging syndromes. A significant decrease in 3-dimensional bone volume fraction (BV/TV) of the fifth lumbar vertebra was observed in AtmKO mice by microCT, compared with heterozygous control mice at 10 weeks of age. Bone histomorphometry revealed that both BFR/BS and Oc.S/BS were significantly decreased in KO mice. To determine the cellular basis of this bone phenotype, we employed in vitro osteoclastogenesis and colony formation assays using bone marrow cells derived from KO and control mice. There was no difference in osteoclast formation in ex vivo cultures. CFU-F was markedly reduced in AtmKO-derived cultures compared with control mice, whereas differentiation of calvaria-derived osteoblasts did not differ between the genotypes. Furthermore, expression levels of IGF1R were significantly decreased, and p38 was aberrantly phosphorylated in marrow stromal cells from AtmKO mice. These results indicate that the pathogenesis of the osteopenic phenotype in AtmKO mice is similar to that of disuse and/or aging syndromes and is caused, at least in part, by a stem cell defect due to lack of IGF signaling.
Rice allergenic proteins, 14-16 kDa albumin and alpha-globulin, remain insoluble in rice grains recovered from rice miso (rice-containing fermented soybean paste).
The rice grains (RG) and rice seed proteins remaining in rice miso were investigated with a view point to the potential allergenicity of rice miso. RG ranging from 36 to 180 mg dry weight per g dry miso were separated from several samples of commercially available rice miso. Scanning electron microscopy of the recovered RG indicated that starch granules disappeared almost completely while protein bodies remained intact in RG. Most of the major seed proteins were extracted from RG by heating with 1% SDS/2% 2-mercaptoethanol and detected by SDS-polyacrylamide gel electrophoresis. Major rice allergenic proteins, 14-16 kDa albumin (Alb14-16) and alpha-globulin (alpha-Glb) were also detected by immunoblotting using the specific antisera, and their contents were estimated to be 1.7 to 9.0 and 1 to 7 mg protein per g dry RG respectively. However, the major rice proteins, including glutelin and prolamin, in RG were insoluble in salt, alcohol, and urea solutions, but soluble in 6 M guanidine hydrochloride (Gu-HCl). By immunoblotting and ELISA, no Alb14-16 and only a slight amount of alpha-Glb were detected even in the 6 M Gu-HCl fraction, indicating that these major allergenic proteins are denatured and are present in an insoluble form in rice miso.
[Can bone quality be assessed non-invasively?--Imaging--].
Properties of "bone quality" contain "structural property" and "material property" . Most components of "material properties" cannot be visualized by current technology. Mineralization, one of material properties, can be evaluated using synchrotron radiation CT or contact microradiography with high spatial and density resolution, but they are invasive examinations. On the other hand, "structural property" can be radiographically delineated, even though only a few methods are available non-invasively. Assessments of macrostructure of bone by radiograms or CT, and trabecular microstructure by high resolution CT or MR can be done non-invasively, and provide valuable results in clinical studies. Bone scintigram provides limited but useful information of bone turnover.
Effect of etidronate on three-dimensional trabecular structure in ovariectomized or sciatic neurectomized rats.
The purpose of this study was to evaluate the effect of etidronate (EHDP) on three-dimensional (3D) trabecular structure in ovariectomized (OVX) and sciatic neurectomized (NX) rats. Eight-week-old female Lewis rats received ovariectomy ( n = 19) or sham operation (OVX-sham; n = 10). OVX rats received either vehicle (OVX-control; n = 9) or EHDP (OVX-EHDP; n = 10). Eight-week-old female Lewis rats received NX ( n = 20) or sham operation (NX-sham; n = 10). NX rats received either vehicle (NX-control; n = 10) or EHDP (NX-EHDP; n = 10). EHDP at 5 mg/kg or vehicle was subcutaneously injected 5 days a week. The treatment was initiated 2 weeks after surgery and was continued for 2 weeks. At 12 weeks of age, the rats were killed, and we scanned the proximal metaphysis of the tibia; this was done using micro-CT; (micro CT20; SCANCO Medical). The recovery of structural parameters was not complete in NX rats compared to OVX rats. The 3D micro-CT images showed that the subcortical spongiosa, which was preserved in OVX rats, had marked loss in NX rats. Furthermore, these trabeculae were not restored after the EHDP treatment. In conclusion, the mechanical driving of the control of trabecular structure is inactive in NX, and EHDP treatment for 2 weeks does not restore this condition.
Regulation of mineral-to-matrix ratio of lumbar trabecular bone in ovariectomized rats treated with risedronate in combination with or without vitamin K2.
The relationship between bone turnover and bone tissue and material properties was examined in ovariectomized (OVX) rats treated with risedronate in combination with or without vitamin K2. Seventy female rats, 18 weeks of age, were assigned to 7 groups (n=10): sham-operated + vehicle control; OVX + vehicle control; OVX + risedronate 0.1, 0.5, or 2.5 mg/kg/day po; OVX + vitamin K2 approximately 30 mg/kg/day po; OVX + vitamin K2 (approximately 30 mg/kg/day) and risedronate (0.5 mg/kg/day). Treatments were given daily for 9 months. To assess bone turnover, we measured serum osteocalcin and urinary deoxypyridinoline at 0, 3, and 9 months. To assess vertebral and femoral tissue and material properties, bone mass, bone mineral density (BMD by DXA), trabecular bone structure (vertebra: 3D-microCT), cortical bone structure (femur: histomorphometry), biomechanical properties, and mineral properties (mineral-to-matrix and carbonate-to-phosphate ratios by Fourier transform infrared microspectroscopy) were measured ex vivo at 9 months. Ovariectomy increased bone turnover and induced significant loss of bone mass/density, structure, mineral properties (mineral-to-matrix ratio), and strength. Risedronate produced dose-dependent inhibition of the ovariectomy-induced increase in turnover and loss of bone mass/density, structure, mineral-to-matrix ratio, and strength, with a lowest effective dose of 0.1-0.5 mg/kg/day. High-dose risedronate (2.5 mg/kg/day) did not induce increases in any parameter above that of sham control. Vitamin K2 had no effects. In the OVX groups, urinary deoxypyridinoline at 3 and 9 months correlated significantly with vertebral BMD, trabecular bone volume, ultimate load, stiffness, and mineral-to-matrix ratio, and with femoral BMD, cortical area, and ultimate load. These results support the concept that changes in bone tissue and material properties can result directly from changes in bone turnover. Different effects among different drugs on material properties, including mineral-to-matrix ratio, may reflect differences in the relative rate and magnitude of osteoclastic bone resorption and osteoblastic primary bone mineralization.
Human parathyroid hormone (1-34) increases mass and structure of the cortical shell, with resultant increase in lumbar bone strength, in ovariectomized rats.
Estrogen deficiency causes reduction of bone mass and abnormal bone microarchitecture, consequently reducing bone strength. Human parathyroid hormone (hPTH) (1-34) increases bone mass and strength. To clarify the factors that determine the recovery of bone strength in the lumbar vertebrae of ovariectomized rats by intermittent hPTH administration, we analyzed the relationship between skeletal measurements and bone strength. Human PTH (1-34) administration resulted in recovery of cortical bone mineral content (BMC) and cortical bone area to sham the levels, but in resulted in a less pronounced recovery of trabecular BMC and no increase in the total cross-sectional area of the vertebral body. Of the three-dimensional (3D) trabecular bone parameters, hPTH (1-34) increased trabecular thickness (Tb.Th). The cortical shell area of L4, determined by histomorphometry, was also increased. In hPTH-treated rats, the only determinant of the compressive load of L5 was the cortical shell BMC, in the early recovery period (days 42-84). Our data suggest that increased cortical bone mass contributes more than trabecular bone mass and structure to the recovery of bone strength in response to hPTH therapy in the rat lumbar vertebral body after ovariectomy.
Effect and safety of intermittent weekly administration of human parathyroid hormone 1-34 in patients with primary osteoporosis evaluated by histomorphometry and microstructural analysis of iliac trabecular bone before and after 1 year of treatment.
In order to evaluate the efficacy and safety of intermittent subcutaneous administration of 1-34 N-terminal peptide of human parathyroid hormone (hPTH 1-34), 100 units of hPTH 1-34 was subcutaneously injected once a week for 1 year in ten patients with primary osteoporsis (one male and nine females) with no qualitative abnormality of the bone according to the results of iliac crest biopsy performed previously, followed by a second biopsy after the end of the 1-year administration. Written consent of the patients for participation in the study was obtained. The mean lumbar bone mineral density (LBMD) definitely increased, by 1.8%, 3.4%, and 4.6% after 12, 24, and 48 weeks of hPTH administration, in accordance with previous clinical studies. Histomorphometric analysis after double-tetracycline labeling was completed in six patients (one male and five females) after the exclusion of those who dropped out because of adverse events unrelated to the test drug, or refusal of continuation. Examination of thin hard-tissue sections revealed no qualitative abnormalities of bone tissue or bone marrow cavity, such as osteomalacia, woven bone, or osteitis fibrosa, precluding the contribution of qualitatively abnormal tissue elements to any changes of LBMD in response to hPTH 1-34 administration. Histomorphometric measurement in the second biopsy revealed a tendency for an increase of bone volume, a significant increase of osteoid surface, and a tendency for an increase in other parameters of bone formation, compared with values obtained in the preadministration biopsy. Indices of two-dimensional microstructure obtained by microfocus computed tomography (CT) and results of node-strut analysis indicated improvement of trabecular continuity. In five patients in whom three-dimensional reconstruction images were analyzed, there were significant increases of bone volume and trabecular thickness, and a significant decrease in the trabecular bone pattern factor, a parameter related to the continuity, suggesting an improvement of the three-dimensional trabcular microstructure. Intermittent weekly subcutaneous injections of hPTH (1-34) for 48 weeks increased trabecular bone volume and improved microstructure, without causing the appearance of abnormal bone elements in primary osteoporosis.
[Assessment of bone quality--present and future].
Bone quality including "structural property" and "material property" , which is strongly affected by bone remodeling and has an influence on bone biomechanical property. Structural property means macroscopical geometry, bone size, trabecular microstructure, cortical thickness and cortical porosity. Material property means mineralization, crystal size, collagen and microdamage. Although most of them are analyzed in vitro, in the future, noninvasive assessment of bone quality may help to guide therapy of osteoporosis.
Which bone densitometry and which skeletal site are clinically useful for monitoring bone mass?
Long-term precision, as well as reproducibility, is important for monitoring bone mineral density (BMD) alteration in response to aging or therapy. In order to investigate which bone densitometry and which skeletal site are clinically useful for monitoring bone mass, we examined the standardized long-term precision of several bone density measurements in 83 healthy Japanese women. Annual BMD measurements were performed for 5 or 6 years using dual X-ray absorptiometry (DXA) on the lumbar spine, radius (EXP5000) and calcaneus (HeelScan); peripheral quantitative computed tomography (pQCT) on the radius (Densiscan1000); and quantitative ultrasound (QUS) on the calcaneus (Achilles+). The long-term precision error for the individual subject was given by the standard error of estimate (SEE), and the standardized long-term precision was defined as the percentage coefficient of variation (CV%) divided by the percentage ratio of the annual bone-loss rate. Based on the CV% of spinal DXA, speed of sound (SOS) and diaphyseal pQCT showed significantly higher precision than others, while radial ultradistal (UD) DXA and heel DXA showed significantly lower precision. The long-term precision errors of other measurements were statistically the same as that of the spinal DXA. The spinal DXA, the radial DXA, and pQCT at both the distal metaphysis and diaphysis showed high rates of annual bone loss. The radial trabecular BMD (pQCT) was significantly higher than that of spinal DXA. The annual rates of bone loss of QUS and of heel DXA were significantly lower than that of spinal DXA. Taken together, standardized long-term precision was obtained in the spinal DXA and radial pQCT. In conclusion, spinal DXA and radial pQCT were considered the most useful monitoring method for osteoporosis, while QUS was considered less useful.
Bone structure and mineralization demonstrated using synchrotron radiation computed tomography (SR-CT) in animal models: preliminary findings.
We investigated the ability of synchrotron radiation computed tomography (SR-CT) to demonstrate trabecular microstructure, detail of trabecular surfaces, and mineralization of bones. Eight rat vertebrae, six rat tibiae, and eight minipig vertebrae were scanned using SR-CT at the synchrotron radiation facility Super Photon ring-8GeV (SPring-8). Images obtained using conventional micro-CT, scanning electron microscopy (SEM), and contact microradiography (CMR) were compared with the SR-CT images. SR-CT showed high image quality without visible partial volume effect. Three-dimensional SR-CT revealed shallow concavities in the bone surface, which were considered to correspond to osteoclastic resorption areas, as well as the connectivity, anisotropy, and shape (rod- or platelike) of trabeculae. Two-dimensional SR-CT showed different density along the surface of the trabecular bone, indicating the degree of bone mineralization. In conclusion, SR-CT seems to be a useful tool for delineating trabecular surfaces, evaluating bone mineralization, and revealing precise trabecular structure.
Reductions in bone turnover, mineral, and structure associated with mechanical properties of lumbar vertebra and femur in glucocorticoid-treated growing minipigs.
The present study was designed to determine the effects of glucocorticoid (GC) on bone turnover, minerals, structure, and bone mechanical properties in minipigs. Six 8-month-old Göttingen minipigs were subcutaneously injected with prednisolone (PN, 0.5 mg/kg body wt (BW)/day, 5 days/week for 26 weeks (Group GC)), 6 were treated with vehicle alone (Group VC), and 4 were sacrificed at start of the study for baseline controls (Group BC). The increase in BW was similar in all groups. PN significantly reduced serum osteocalcin and urinary type-1 collagen N-telopeptide levels at 13 weeks and thereafter, compared with baseline and control, and also reduced serum bone specific alkaline phosphatase levels relative to baseline. At 26 weeks, the longitudinal axis of the lumbar bone and length of femur were smaller in Group GC than Group VC. The total cross-sectional area of femur, but not the lumbar bone, in Group GC was significantly different from Group VC. BMD of the femur, but not L2, measured by DXA, was lower in Group GC than in Groups BC and VC. The cortical shell structure measured by 2D-micro-CT deteriorated and age-dependent increases in trabecular bone structure 3D micro-CT were reduced by PN. PN also caused deterioration of the cortical structure of the mid-femur. In L2 and femur, PN significantly reduced the ultimate load and maximum absorption energy of the femur and L2 compared with Group VC. The structural modulus in Group GC was lower than in Group BC. Regression analyses revealed that bone minerals, bone structure, and chemical markers correlated with mechanical properties of L2 and mid-femur. Our results indicate that PN reduced systemic bone formation and resorption and suppressed the age-dependent increases in bone minerals, structure, and mechanical properties of L2 and mid-femur. Reduced bone turnover seemed to be associated with a reduction in mechanical properties. The growing minipig could be a suitable model of GCs-induced osteoporosis in humans.
Long-term treatment of incadronate disodium accumulates microdamage but improves the trabecular bone microarchitecture in dog vertebra.
This study aimed to investigate the effect of long-term suppression of bone resorption by bisphosphonate on the microstructure, accumulation of microdamage, and mechanical properties of trabecular bone. Twenty-nine 1-year-old beagles (15 males, 14 females) were divided into three groups. The control group (CNT) was treated daily with vehicle, and the other two groups were treated with incadronate at a dose of 0.3 mg/kg/day (LOW) or 0.6 mg/kg/day (HIGH) orally for 3 years. After death, the second thoracic vertebra was scanned with microcomputed tomography (micro-CT) and assigned to histomorphometric and microdamage measurements. The fourth lumbar vertebra was mechanically tested by compression. Incadronate concentration in bone was measured in the 11th thoracic vertebra. Micro-CT analysis demonstrated a platelike trabecular structure and increased concave surface of trabeculae in the thoracic vertebra of incadronate-treated groups. Three-year incadronate treatment significantly suppressed trabecular activation rates by 56% in LOW and 67% in HIGH without impairment of mineralization, and increased microdamage accumulation in both incadronate-treated groups. Trabecular bone volume was significantly increased in both LOW and HIGH groups, and vertebral strength was significantly increased in the HIGH group compared with the CNT group. However, intrinsic material properties such as normalized ultimate stress and normalized toughness were reduced in incadronate-treated groups. Incadronate concentration in bone was dose-dependent. This study suggests that long-term suppression of bone remodeling increases microdamage accumulation, but this is not necessarily associated with vertebral fragility because of compensated increase of bone mass and improved microarchitecture.
[Effects of bisphosphonate on trabecular microstructure].
Bisphosphonate is known to be deposited in resorption area. In our small animal study to evaluate the effect of bisphosphonate on trabecular microstructure, micro-CT demonstrated the different trabecular microstructure among the sham, ovariectomized (OVX) rats and the OVX rats which were treated with risedronate (0.1, 0.5, 2.5 mg/kg) or menatetrenone 30 mg/kg, or with the combination of risedronate 0.5 mg/kg and menatetrenone 30 mg/kg. The pattern of change on trabecular microstructure was also different between risedronate and menatetrenone; risedronate maintained trabecular connectivity, whereas menatetrenone thickened the trabeculae. The combination therapy with menatetrenone provided an additional improvement of trabecular microstructure to the single use of risedronate.
[Involvement of Daikou Sunabashi Clinic in home care to home death].
Daikou Sundabashi Clinic provides continuous advanced medical treatment and visiting nursing services for patients with serious diseases till their death at home. The clinic has been involved in home care of 72 patients in total during the period from April 2002 to July 1 of 2003. Of the patients, 40 patients died to date and 71% (32 patients) of them died at home. 49 of the 72 patients (70%) had terminal cancer and mostly required advanced home care. The clinic provides services according to the following principles till the death of the patients: 1. All of our medical staff pool their information and stay in very close communication with one another. 2. The attending physician gives a complete explanation of the patient's condition to his/her family. 3. The staffs respond to emergency calls around the clock using 2 cell phones. Under this very meticulous and fast-response system, seriously ill patient can receive continuous and high-quality treatment at home and die at home even if the family is not adequately capable of providing care.