Hideo Okumura

Identification of peak bone mass QTL in a spontaneously osteoporotic mouse strain

Abstract. The whole genome scan for quantitative trait loci (QTLs) specifying peak bone mass was performed with the F2 intercrosses of SAMP6, an established murine model of senile osteoporosis, exhibiting a significantly lower peak bone mass, and SAMP2, exhibiting a higher peak bone mass. Cortical thickness index (CTI), a parameter of bone mass of femurs, was measured in 488 F2 progeny at 4 months of age, when the animals attained peak bone mass by microphotodensitometry. Genetic markers were typed at 90 loci spanning all chromosomes except the Y. By interval mapping of 246 male F2 mice, two loci were identified with significant linkage to peak bone mass, one on Chromosome (Chr) 11 and another on Chr 13, with a maximum lod score of 10.8 (22.2% of the total variance) and 5.8 (10.0%), respectively. Another locus on the X Chr was suggestive of a QTL associated oppositely with a low peak bone mass to the SAMP2 allele. This association was consistent with the distribution of peak bone mass in the F1 and F2. These findings should be useful to elucidate the genetics of osteoporosis.

Delayed neuronal damage related to microglia proliferation after mild spinal cord compression injury

In order to investigate the mechanism of delayed progressive or secondary neuronal damage after the spinal cord injury, we developed a mild-compression injury model in the rat thoracic spinal cord. Our compression device consists of a soft silicone point of contact to the dura, in order to prevent violent injury that may cause axonal tears or hemorrhages in the spinal cord. Since rats often assume a standing posture, i.e. raising head with lifting their fore-limbs, damage to the thoracic spinal cord was evaluated by measuring the frequency of standing, which effectively indicates hind limb function. Twenty-four hours after compression by a 20 g weight for 10 or 20 min, the standing frequency of the injured rat was almost the same as that of sham animals that underwent laminectomy without compression. However, the standing frequency decreased with time; the frequency of standing at 72 h was approximately 30-50% that of sham animals. In the compressed spinal cord tissue, microglial cells, detected by lectin staining, proliferated with time. An enormous amount of microglia was observed at 48 and 72 h after compression, although only a small amount of cells were positive to lectin staining at 24 h after the compression. These results suggest that our mild-compression spinal cord injury model showed late-onset or delayed neuronal damage that may be related to pathological microglia proliferation.

Cemented total hip arthroplasty with acetabular bone graft for developmental dysplasia

Although the technique of autogenous acetabular bone grafting has been widely used to augment containment of the acetabulum in total hip arthroplasty (THA) for developmental dysplasia, the role of this technique in improving long-term results remains controversial.nnWe present the long-term results of cemented THA with acetabular bone grafting in 112 patients (133 hips) in order to clarify the factors which affect the outcome. The mean follow-up was for 12.3 years (8 to 24). Kaplan-Meier survivorship analysis predicted a rate of survival of the acetabular component at 15 years of 96% (95% confidence interval (CI) 92 to 99) with revision for aseptic loosening as the endpoint, and of 75% (95% CI 65 to 85) when radiological loosening was used. Parametric survivorship analysis using the Cox proportional-hazards model indicated that trochanteric nonunion, lateral placement of the socket, and delayed trabecular reorientation of the bone graft were risk factors for loosening of the acetabular component.nnOur findings have shown that autologous acetabular bone grafting is of value for long-term success provided that the risk factors are reduced.

Cementless total hip replacement. Bio-active glass ceramic coating studied in dogs.

We studied 2 types of a cementless total hip prosthesis in dogs. Both were coated with titanium plasma-spray. In both components, the pores in the deep layer of 1 group were further coated with apatite and wollastonite containing glass-ceramic (AW glass-ceramic). 50 dogs underwent unilateral total hip replacements, and were killed at 1, 3, or 6 months postoperatively. We evaluated the femoral and the acetabular components mechanically and histologically. At 1 month, the detaching load and bone ingrowth of the AW glass-ceramic-coated femoral and acetabular components were higher than those of the control implants. At 3 and 6 months there were no differences between the 2 types of components. Thus, AW glass-ceramic enhanced the early phase of cementless implant fixation.

Existence of Lipoprotein Lipase in Human Sarcomas and Carcinomas

Aqueous extracts of acetone/ether powders of surgically obtained specimens of human tumors hydrolyzed 3H‐labeled triolein in a dose‐dependent manner. The lipolytic activity in these extracts was inhibited by anti‐lipoprotein lipase (LPL) IgG dose‐dependently, 25 μg of anti‐LPL IgG causing 95% inhibition of the activity. Thus, LPL accounts for most of the lipolytic activity in extracts of acetone/ether powders of the tumors. All sarcomas and carcinomas examined contained LPL activity. Western blotting showed that they gave a band corresponding to that of human adipose tissue LPL (Mr=57,000). Immunocytochemical studies showed that LPL was present in cultured human osteosarcoma cells and distributed throughout the cells. We determined the proliferating cell nuclear antigen (PCNA)‐labeling index as an indicator of the proliferative activity of tumor cells and measured LPL activity in extracts of tumors in areas corresponding to those used for determining the PCNA‐labeling index. In malignant fibrous histiocytomas, the PCNA‐labeling index in area a, which corresponds to the subcapsular region, was higher than that in area b, which corresponds to the central region. The LPL activity in area a was 10 times that in area b. In rectal cancer, the index in area c, which corresponds to the subserosal region, was higher than that in area d, which corresponds to the submucosal region. The LPL activity in area c was 1.9 times that in area d. These findings indicate heterogeneity in the distributions of LPL activity within tumors and higher levels of LPL activity in tumors that are proliferating actively.

The effect of active vitamin D3 analogs and dexamethasone on the expression of osteocalcin gene in rat tibiae in vivo

We tested the effects of 1 alpha,25-dihydroxyvitamin D3 (1,25-(OH)2D3), 2 beta-(3-hydroxypropoxy)-1 alpha,25-dihydroxyvitamin D3 (ED-71) and dexamethasone on osteocalcin mRNA levels in rat tibiae in vivo. Northern blot analysis showed that both 1,25-(OH)2D3 and ED-71 caused an increase in osteocalcin mRNA levels in bone: 1,25-(OH)2D3 induced a transient increase in the mRNA levels followed by a decrease in the control level by 12 h post administration. In contrast, ED-71 caused a persistent increase in osteocalcin mRNA level for seven days post administration. Serum osteocalcin levels paralleled the osteocalcin mRNA level in bone in both groups. Dexamethasone caused a marked reduction in both osteocalcin mRNA and serum osteocalcin levels. Suppressive effect of dexamethasone on osteocalcin expression was persistent for seven days at higher dose. Our results represent the first demonstration of the effect of active vitamin D and corticosteroid on the expression of osteocalcin mRNA in bone in vivo.

Femoral component made of Ti-15Mo-5Zr-3Al alloy in total hip arthroplasty

We have developed a femoral component made of Ti-15Mo-5Zr-3Al alloy for total hip prostheses. In vitro mechanical experiments showed that this alloy had better mechanical properties than Ti-6Al-4V alloy with respect to yield strength, tensile strength, elongation, and reduction of area. The elastic modulus of the Ti-15Mo-5Zr-3Al alloy was lower than and its fatigue properties were superior to those of the Ti-6Al-4V alloy. Intraosseous implantation experiments in vivo revealed favorable bone formation around the implants made of Ti-15Mo-5Zr-3Al in rat tibia and no inflammatory responses to the implant. Ti-15Mo-5Zr-3Al alloy appears to be a suitable material for the femoral components of total hip prostheses.

Modification of strain-specific femoral bone density by bone marrow-derived factors administered neonatally: a study on the spontaneously osteoporotic mouse, SAMP6.

SAMP6 is a recently developed strain of osteoporotic mice, and SAMP2 is a control for SAMP6 and has a higher peak bone mass. The bone mass of SAMP6 was increased until 2 months of age when a lysate of cells derived from the bone marrow of SAMP2 was injected at 1 or 4 days of age, but it was not increased when the lysate was injected at 21 days of age. No effect on bone mass was observed when lysates of other cells, bovine serum albumin or heat-inactivated lysate of bone marrow-derived cells of SAMP2, were injected. The ability to increase bone mass was not in the supernatant but in the pellet obtained by ultracentrifugation (105,000 g) of the lysate of bone marrow-derived cells of SAMP2. The lysate did not change the osteoclast surface but changed the appositional bone formation. In conclusion, the lysate of cells derived from the bone marrow of SAMP2 contains factors which can increase the bone mass of SAMP6, and these factors are present in the pellet obtained by ultracentrifugation.

Effective intervention of low peak bone mass and bone modeling in the spontaneous murine model of senile osteoporosis, SAM-P/6, by Ca supplement and hormone treatment

SAM-P/6 is a recently developed strain of osteoporotic mice. In this study we tried to determine whether calcium, vitamin D3, parathyroid hormone (PTH), and estrogen modified the peak bone mass of young SAM-P/6 mice, and whether the effect of these medications persisted after treatment had been discontinued. Calcium supplement, PTH, and estrogen treatment increased the peak bone mass of SAM-P/6 mice. To clarify the process by which bone mass was increased in these treated mice, we evaluated their bone formation and resorption by histomorphometry and measured the levels of ions and serum enzymes relevant to bone metabolism. We found that bone formation was increased by calcium supplementation, and bone resorption was decreased by estrogen treatment. Furthermore, the effectiveness of calcium supplement on peak bone mass was retained after treatment had been discontinued, but the effect of estrogen treatment on peak bone mass was reduced after estrogen treatment had been discontinued. The results of this study indicate that calcium supplementation and estrogen and PTH treatment each increased peak bone mass at the midpoint of the femur of SAM-P/6, and that the effect of calcium supplementation, but not that of estrogen treatment, persisted after treatment was discontinued.

Severe metallosis due to abnormal abrasion of the femoral head in a dual-bearing hip prosthesis : a case report

The authors report on a patient with a case of severe metallosis due to an abnormal abrasion of the femoral head. A primary arthroplasty was performed using a dual bearing hip prosthesis with acetabular bone grafting by ceramic screws. At the time of the revision surgery the synovia was black, and an analysis using a scanning electron microscope and scanning electron microscope-electron probe micro-analyzer revealed numerous small particles of small alumina ceramic on the inner surface of the bearing insert of high-density polyethylene. These particles, which came from the broken ceramic screws due to proximal migration of the prosthesis, scraped the femoral head away. A line and area analysis of the black synovia revealed that the synovia contained metal particles of a cobalt-chromium alloy as well as a cobalt ion. The patients serum showed elevated concentrations of cobalt, chromium, and molybdenum that dramatically reduced 2 months after the revision surgery.