Bone biopsy findings in patients receiving long-term bisphosphonate therapy for glucocorticoid-induced osteoporosis.

INTRODUCTION: Bisphosphonates (BPs) have been shown to reduce the incidence of vertebral fractures during the first year or two of glucocorticoid (GC) treatments and are therefore recommended as a first-line treatment for GC-induced osteoporosis (GIO). However, there are theoretical concerns about the long-term use of BPs in low-turnover osteoporosis caused by chronic GC therapy. MATERIALS AND METHODS: We analyzed the trabecular microarchitecture, bone metabolism, and material strength of iliac crest bone biopsy samples from 10 female patients with rheumatoid arthritis who received an average of 6.7 years of BP therapy for GIO (GIOBP group), compared with those of 10 age- and bone mineral density (BMD)-matched non-rheumatoid arthritis postmenopausal women (reference group). RESULTS: Patients in the GIOBP group had a significantly greater fracture severity index, as calculated from the number and the extent of vertebral fractures compared with the reference patients. Micro-computed tomography analysis showed that the degree of mineralization and trabecular microarchitecture were significantly lower in the GIOBP group than in the reference patients. Patients in the GIOBP group exhibited lower bone contact stiffness, determined by micro-indentation testing, than in the reference group. The contact stiffness of the bone was negatively correlated with the fracture severity index and the daily prednisolone dosage. Immunohistochemistry and serum bone turnover markers showed decreased osteoclastic activity, impaired mineralization, and an increased fraction of empty lacunae in the GIOBP group. CONCLUSION: Our findings indicate that patients receiving long-term BP for GIO are still at high risk for fragility fractures because of poor bone quality.

Mechanical Properties of Human Concentrated Growth Factor (CGF) Membrane and the CGF Graft with Bone Morphogenetic Protein-2 (BMP-2) onto Periosteum of the Skull of Nude Mice.

Concentrated growth factor (CGF) is 100% blood-derived, cross-linked fibrin glue with platelets and growth factors. Human CGF clot is transformed into membrane by a compression device, which has been widely used clinically. However, the mechanical properties of the CGF membranes have not been well characterized. The aims of this study were to measure the tensile strength of human CGF membrane and observe its behavior as a scaffold of BMP-2 in ectopic site over the skull. The tensile test of the full length was performed at the speed of 2mm/min. The CGF membrane (5 × 5 × 2 mm3) or the CGF/BMP-2 (1.0 µg) membrane was grafted onto the skull periosteum of nude mice (5-week-old, male), and harvested at 14 days after the graft. The appearance and size of the CGF membranes were almost same for 7 days by soaking at 4 °C in saline. The average values of the tensile strength at 0 day and 7 days were 0.24 MPa and 0.26 MPa, respectively. No significant differences of both the tensile strength and the elastic modulus were found among 0, 1, 3, and 7 days. Supra-periosteal bone induction was found at 14 days in the CGF/BMP-2, while the CGF alone did not induce bone. These results demonstrated that human CGF membrane could become a short-term, sticky fibrin scaffold for BMP-2, and might be preserved as auto-membranes for wound protection after the surgery.

Magnetic resonance imaging T1 and T2 mapping provide complementary information on the bone mineral density regarding cancellous bone strength in the femoral head of postmenopausal women with osteoarthritis.

BACKGROUND: Since bone mass is not the only determinant of bone strength, there has been increasing interest in incorporating the bone quality into fracture risk assessments. We aimed to examine whether the magnetic resonance imaging (MRI) T1 or T2 mapping value could provide information that is complementary to bone mineral density for more accurate prediction of cancellous bone strength. METHODS: Four postmenopausal women with hip osteoarthritis underwent 3.0-T MRI to acquire the T1 and T2 values of the cancellous bone of the femoral head before total hip arthroplasty. After the surgery, the excised femoral head was portioned into multiple cubic cancellous bone specimens with side of 5 mm, and the specimens were then subjected to microcomputed tomography followed by biomechanical testing. FINDINGS: The T1 value positively correlated with the yield stress (σy) and collapsed stress (σc). The T2 value did not correlate with the yield stress, but it correlated with the collapsed stress and strength reduction ratio (σc/σy), which reflects the progressive re-fracture risk. Partial correlation coefficient analyses, after adjusting for the bone mineral density, showed a statistically significant correlation between T1 value and yield stress. The use of multiple coefficients of determination by least squares analysis emphasizes the superiority of combining the bone mineral density and the MRI mapping values in predicting the cancellous bone strength compared with the bone mineral density-based prediction alone. INTERPRETATION: The MRI T1 and T2 values predict cancellous bone strength including the change in bone quality.

A Novel Bone Marrow Stimulation Technique Augmented by Administration of Ultrapurified Alginate Gel Enhances Osteochondral Repair in a Rabbit Model.

Cartilage injuries are a common health problem resulting in the loss of daily activities. Bone marrow stimulation technique, one of the surgical techniques for the cartilage injuries, is characterized by technical simplicity and less invasiveness. However, it has been shown to result in fibrous or fibrocartilaginous repair with inferior long-term results. This study focused on using ultrapurified alginate gel (UPAL gel) as an adjuvant scaffold in combination with a bone marrow stimulation technique. The objective of this study was to assess the efficacy of a bone marrow stimulation technique augmented by UPAL gel in a rabbit osteochondral defect model. To achieve this goal, three experimental groups were prepared as follows: defects without intervention, defects treated with a bone marrow stimulation technique, and defects treated with a bone marrow stimulation technique augmented by UPAL gel. The macroscopic and histological findings of the defects augmented by UPAL gel improved significantly more than those of the others at 16 weeks postoperatively. The combination technique elicited hyaline-like cartilage repair, unlike bone marrow stimulation technique alone. This combination procedure has the potential of improving clinical outcomes after use of a bone marrow stimulation technique for articular cartilage injuries.

Therapeutic effects of intra-articular ultra-purified low endotoxin alginate administration on an experimental canine osteoarthritis model.

OBJECTIVE: This study aimed to elucidate the therapeutic effects of intra-articular administration of ultra-purified low endotoxin alginate (UPLE-alginate) on osteoarthritis (OA) using a canine anterior cruciate ligament transection (ACLT) model. DESIGN: We used 20 beagle dogs. ACLT was performed on the left knee of each dog and a sham operation was performed on the right knee as a control. All animals were randomly divided into the control (saline) and therapeutic (UPLE-alginate) groups. Animals in the control and therapeutic groups received weekly injections with 0.7 mL normal saline or 0.7 mL 0.5% UPLE-alginate, respectively, from 0 to 3 weeks after ACLT or sham operation. At 9 weeks after ACLT, the knee joints of all animals were observed using arthroscopy. All animals were euthanized at 14 weeks after ACLT and evaluated using morphologic assessment, histologic assessment, and biomechanical testing. RESULTS: Arthroscopic findings showed intact cartilage surface in both groups. Morphologic findings in the therapeutic group showed milder degeneration compared with those of the control group, but there were no significant differences between groups. Histologic scores of the medial femoral condyle (MFC) and lateral femoral condyle (LFC) were better in the therapeutic group than the control group (MFC: p = 0.009, LFC: p = 0.009). Joint lubrication did not differ significantly between groups. CONCLUSION: Intra-articular administration of UPLE-alginate in the early stage of OA slowed disease progression in canines. UPLE-alginate may have potential as a therapeutic agent for OA patients and reduce the number of patients who need to undergo total joint arthroplasty.

Vitamin K-dependent carboxylation of osteocalcin affects the efficacy of teriparatide (PTH(1-34)) for skeletal repair.

Teriparatide (PTH1-34) promotes skeletal repair and increases bone mass. Vitamin K is involved in bone mineralization as a coenzyme of γ-carboxylase for Gla proteins, and therefore vitamin K insufficiency caused by malnutrition or therapeutic intake of the vitamin K antagonist warfarin could affect the efficacy of PTH1-34 therapy for bone repair. In the present study, we investigated whether vitamin K influences the efficacy of PTH1-34 therapy for bone repair in a rat osteotomy model. Female 12-week-old Sprague-Dawley rats were subjected to a closed midshaft osteotomy of the femur and randomized into four groups (n=10 per group): vehicle, PTH1-34 (daily 30 µg/kg/day subcutaneous injection)+solvent (orally, three times a week), PTH1-34+warfarin (0.4 mg/kg/day orally, three times a week), and PTH1-34+vitamin K2 (menatetrenone, 30 mg/kg/day orally, three times a week). Serum γ-carboxylated and uncarboxylated osteocalcin (Gla-OC and Glu-OC) levels and radiographic healing were monitored every 2 weeks. Skeletal repair was assessed by micro-computed tomography, mechanical testing, and histology at 8weeks after surgery. PTH1-34 amplified the osteotomy-induced increase in Gla-OC and improved the mechanical properties as well as the volumetric bone mineral tissue density of the fracture callus. Concurrent use of warfarin decreased the response to PTH1-34 therapy in terms of mechanical recovery, probably by impairing mineralization due to the lack of Gla-OC. Although the effects of combination therapy with PTH1-34 and vitamin K2 on bone repair did not significantly exceed those of PTH1-34 monotherapy in rats fed sufficient dietary vitamin K, postoperative Gla-OC levels were correlated with the mechanical properties of the osteotomized femur in PTH1-34-treated rats regardless of the use of warfarin or vitamin K2. These findings suggest the importance of vitamin K dependent γ-carboxylation of OC for realizing the full effects of PTH1-34 on skeletal repair.

Monochromatic synchrotron radiation muCT reveals disuse-mediated canal network rarefaction in cortical bone of growing rat tibiae.

The purpose of this study was to demonstrate the ability of computed microtomography based on monochromatic synchrotron radiation (SRmuCT) in microstructural analysis of cortical bone. Tibial diaphyses of growing rats (14 wk, n = 8) undergoing unilateral sciatic neurectomy 8 wk before study were imaged with spatial volume resolution of 5.83 x 5.83 x 5.83 microm3 by SRmuCT (20 keV) at the synchrotron radiation facility (SPring-8). Reconstructed image data were translated into local mineral densities by using a calibrated linear relationship between linear absorption coefficients and concentrations of homogeneous K2HPO4 solution. Pure bone three-dimensional images, produced by simple thresholding at a bone mineral density of 0.82 g/cm3, were analyzed for macro- and microscopic structural properties. In neurectomized hindlimbs, cortical canal network rarefaction as well as bone atrophy were found. The former was characterized by 30% smaller porosity, 11% smaller canal density in transverse section, and 38% smaller canal connectivity density than those in contralateral bone. On the other hand, no difference was found in bone mineral density between neurectomized and intact hindlimbs (1.37 vs. 1.36 g/cm3). In conclusion, SRmuCT is a promising method for the three-dimensional analysis of cortical microstructure and the degree of mineralization in small animals.