Biomedical subjects

Hidehiko Higaki

Publications and source records attributed to Hidehiko Higaki.

7 recordsLinked to original sources

PubMed2006

Bone marrow cell differentiation induced by mechanically damaged osteocytes in 3D gel-embedded culture.

UNLABELLED: Osteocytes are suggested to have a crucial role in the initial resorptive phase of bone turnover after microdamage. To study the role of osteocytes in targeted remodeling, we developed an in vitro model, in which osteocytes can be locally damaged and their interactions with bone marrow cells studied. Our results show that the damaged osteocytes activate the osteoclast precursors by soluble factors and thus can control the initial phase of targeted remodeling. INTRODUCTION: Microdamage in bone contributes to fractures and acts as a stimulus for bone remodeling. Besides the targeted remodeling, some remodeling may also be random to serve metabolic purposes. Osteocytes have been considered to provide a crucial role in the activation of osteoclastic bone resorption adjacent to the damaged site. This study was aimed to develop a relevant in vitro model of the targeted remodeling and to show that damaged osteocytes can induce the initial bone resorptive stage. MATERIALS AND METHODS: We developed a new device, in which osteocyte-like cell line MLO-Y4 cells were 3D cultured, subjected to local scratching, and assayed for cell viability. NIH3T3-3 cells were used as a control. Bone marrow cells were cultured on the top of the mechanically damaged MLO-Y4 cells, and the formation of TRACP+ cells was assayed. Additionally, the conditioned medium from scratched cultures was added to bone marrow cultures, and the TRACP activity in cell lysates was quantified. The macrophage-colony stimulating factor (M-CSF) and RANKL secretion in the conditioned medium was assayed by ELISA. RESULTS: Scratching induced the death of MLO-Y4 cells. When bone marrow cells were cultured over the gel-embedded MLO-Y4 cells, the application of mechanical scratching induced TRACP+ cell differentiation on gel surface. The cells with TRACP+ could be observed in the very restricted region along the scratching path. Additionally, mechanically damaged osteocytes secreted M-CSF and RANKL, and the conditioned medium showed the potential to induce TRACP+ cells in bone marrow culture. CONCLUSIONS: These findings indicate that soluble factors secreted from damaged osteocytes can locally induce and activate the initial phase of osteoclastic cell formation. This study directly shows the association between the damaged osteocytes and the initiation of resorptive stage in bone remodeling.

Animals↗

PubMed2006

The effect of ankle rotation on cutting of the tibia in total knee arthroplasty.

BACKGROUND: Extramedullary alignment guides are commonly used to prepare the tibia during total knee arthroplasty. One disadvantage is that the guide is easily affected by the position of the ankle joint. The tibia may have a rotational mismatch between its proximal and distal ends. We hypothesized that a rotational mismatch might cause incorrect positioning of an extramedullary alignment guide and evaluated such a mismatch on the predicted postoperative coronal alignment of the tibia. METHODS: Fifty-three osteoarthritic knees with varus deformity in fifty-one patients were evaluated with use of computerized tomography scans before total knee arthroplasty. We defined one anteroposterior axis of the ankle joint and five different anteroposterior axes of the proximal aspect of the tibia using three-dimensional bone models from the computerized tomography data. We measured the rotational angle between the anteroposterior axis of the ankle joint and the proximal part of the tibia. The distal end of the extramedullary guide was placed in front of the center of the ankle joint (on the line of the extended anteroposterior axis of the ankle joint), and the proximal end was placed on the line of the extended anteroposterior axis of the proximal part of the tibia. We established spatial coordinates to evaluate the effect of the rotational angle on the predicted postoperative coronal alignment of the tibia and calculated the presumed tibial coronal alignment. RESULTS: The rotational angle was positive (3.6 degrees to 19.7 degrees) for all of the anteroposterior axes of the proximal aspect of the tibia, indicating that the ankle joint was externally rotated relative to the proximal part of the tibia. The predicted tibial coronal alignment was varus (0.5 degrees to 5.1 degrees) for all of the anteroposterior axes of the proximal part of the tibia. CONCLUSIONS: When an extramedullary alignment guide is used to prepare the tibia in total knee arthroplasty, varus alignment of the tibial component can occur because of a rotational mismatch between the proximal part of the tibia and the ankle joint.

Aged↗

PubMed2006

Repetitive tensile stress to rat caudal vertebrae inducing cartilage formation in the spinal ligaments: a possible role of mechanical stress in the development of ossification of the spinal ligaments.

OBJECT: Mechanical stress has been considered one of the important factors in ossification of the spinal ligaments. According to previous clinical and in vitro studies, the accumulation of tensile stress to these ligaments may be responsible for ligament ossification. To elucidate the relationship between such mechanical stress and the development of ossification of the spinal ligaments, the authors established an animal experimental model in which the in vivo response of the spinal ligaments to direct repetitive tensile loading could be observed. METHODS: The caudal vertebrae of adult Wistar rats were studied. After creating a novel stimulating apparatus, cyclic tensile force was loaded to rat caudal spinal ligaments at 10 N in 600 to 1800 cycles per day for up to 2 weeks. The morphological responses were then evaluated histologically and immunohistochemically. After the loadings, ectopic cartilaginous formations surrounded by proliferating round cells were observed near the insertion of the spinal ligaments. Several areas of the cartilaginous tissue were accompanied by woven bone. Bone morphogenetic protein-2 expression was clearly observed in the cytoplasm of the proliferating round cells. The histological features of the rat spinal ligaments induced by the tensile loadings resembled those of spinal ligament ossification observed in humans. CONCLUSIONS: The findings obtained in the present study strongly suggest that repetitive tensile stress to the spinal ligaments is one of the important causes of ligament ossification in the spine.

Animals↗

PubMed2004

[Bone quantity and quality to its mechanical integrity].

Bone strength is made up of quantity (mass, mineralization), geometry (anatomy, micro architecture, collagen structure), and turnover/damage accumulation. While most of the mechanical behavior can be explained by measures of porosity, several additional descriptors of the geometry have been proposed for better predictions of fracture risk. This review introduces various aspects of these relationships between bone quantity and quality to its mechanical integrity.

Biomechanical Phenomena↗

PubMed2003

Mechanical effects of the intraarticular administration of high molecular weight hyaluronic acid plus phospholipid on synovial joint lubrication and prevention of articular cartilage degeneration in experimental osteoarthritis.

OBJECTIVE: To examine in vivo the effects of a mixture of high molecular weight hyaluronic acid (HA) plus phospholipids on joint lubrication and articular cartilage degeneration. METHODS: Experimental osteoarthritis (OA) of the right knee was induced by anterior cruciate and medial collateral ligament transection in 40 rabbits. The animals were subjected to 8 consecutive weekly intraarticular administrations of high molecular weight HA (the HA200 group), conventional molecular weight HA (the HA80 group), or high molecular weight HA plus L-delta dipalmitoyl phosphatidylcholine liposomes (the PHA group) and were killed 1 week after the final injection. The remaining transected right knees (the OA group) and randomly selected nontransected contralateral left knees (the control group) were collected simultaneously. Each group (n = 10) was divided into 2 equal subgroups, one of which was evaluated histologically while the other was subjected to a lubricating ability test using a pendulum friction tester. RESULTS: The injected knees had a tendency to demonstrate less damage to the articular cartilage compared with the OA group, and the histologic findings in all groups except for the PHA group differed significantly from the control group. There was a significant difference in the mean +/- SD friction coefficient between the control group (0.0100 +/- 0.00300) and the OA (0.0206 +/- 0.00649), HA200 (0.0190 +/- 0.00427), and HA80 (0.0177 +/- 0.00712) groups (P < 0.05 for each comparison), but not between the control group and the PHA group (0.0150 +/- 0.00330) (P = 0.15). CONCLUSION: To our knowledge, this is the first in vivo study to examine whether intraarticular injections of phospholipids influence joint lubrication by acting as a boundary lubricant, thus protecting articular cartilage from degenerative changes.

Animals↗

PubMed2002

Prediction of total knee arthroplasty polyethylene wear using the wear index.

The predictive value of the wear index for total knee arthroplasty polyethylene wear was determined using a numeric and in vitro model. The wear index was defined as the deformation x the sliding velocity. Four commercially available total knee prostheses were modeled for this study. Deformation and sliding velocity were calculated from the 3-dimensional geometry of the components and the gait kinematic inputs using Hertz's formula. A knee simulation test was performed under the same conditions, and the surface of the inserts was compared with the wear index. This study showed good agreement between the numeric model and the simulation test, suggesting that the wear index is a reliable predictor of total knee arthroplasty polyethylene wear through its incorporation of contact stress and kinematics.

Arthroplasty, Replacement, Hip↗

PubMed2002

Patellar tracking and patellofemoral geometry in deep knee flexion.

Patellar tracking and femoral condylar geometry in deep knee flexion were evaluated using magnetic resonance imaging. The patellar tilting angle, patellar shift, and patellar anteroposterior translation from 0 degrees to 135 degrees flexion were measured. The depth of the femoral condylar articular surface and the curvature of the femoral condylar articular surface also were measured at 135 degrees flexion. The patella shifted laterally, tilted medially, and sank deeply into the intercondylar notch during deep knee flexion. The articular surface of the lateral condyle, existing deep within the intercondylar notch, began to curve steeply at a point farther from the center of the intercondylar notch than did the medial condyle. The geometry of the femoral condyle is adequate to fit the patellar geometry. Results of the current study suggest that the geometry of the lateral femoral condyle allows the patella to track smoothly with a larger patellofemoral contact area and less patellofemoral pressure during deep flexion.

Adult↗