Bungo Otsuki

Osteoblast-Targeted Expression of Sfrp4 in Mice Results in Low Bone Mass†‡

Transgenic mice overexpressing Sfrp4 in osteoblasts were established. These mice exhibited low bone mass caused by a decrease in bone formation.

Wwp2 is essential for palatogenesis mediated by the interaction between Sox9 and mediator subunit 25.

Sox9 is a direct transcriptional activator of cartilage-specific extracellular matrix genes and has essential roles in chondrogenesis. Mutations in or around the SOX9 gene cause campomelic dysplasia or Pierre Robin Sequence. However, Sox9-dependent transcriptional control in chondrogenesis remains largely unknown. Here we identify Wwp2 as a direct target of Sox9. Wwp2 interacts physically with Sox9 and is associated with Sox9 transcriptional activity via its nuclear translocation. A yeast two-hybrid screen using a cDNA library reveals that Wwp2 interacts with Med25, a component of the Mediator complex. The positive regulation of Sox9 transcriptional activity by Wwp2 is mediated by the binding between Sox9 and Med25. In zebrafish, morpholino-mediated knockdown of either wwp2 or med25 induces palatal malformation, which is comparable to that in sox9 mutants. These results provide evidence that the regulatory interaction between Sox9, Wwp2 and Med25 defines the Sox9 transcriptional mechanisms of chondrogenesis in the forming palate.

Effect of pore size on bone ingrowth into porous titanium implants fabricated by additive manufacturing: An in vivo experiment.

Selective laser melting (SLM) is an additive manufacturing technique with the ability to produce metallic scaffolds with accurately controlled pore size, porosity, and interconnectivity for orthopedic applications. However, the optimal pore structure of porous titanium manufactured by SLM remains unclear. In this study, we evaluated the effect of pore size with constant porosity on in vivo bone ingrowth in rabbits into porous titanium implants manufactured by SLM. Three porous titanium implants (with an intended porosity of 65% and pore sizes of 300, 600, and 900μm, designated the P300, P600, and P900 implants, respectively) were manufactured by SLM. A diamond lattice was adapted as the basic structure. Their porous structures were evaluated and verified using microfocus X-ray computed tomography. Their bone-implant fixation ability was evaluated by their implantation as porous-surfaced titanium plates into the cortical bone of the rabbit tibia. Bone ingrowth was evaluated by their implantation as cylindrical porous titanium implants into the cancellous bone of the rabbit femur for 2, 4, and 8weeks. The average pore sizes of the P300, P600, and P900 implants were 309, 632, and 956μm, respectively. The P600 implant demonstrated a significantly higher fixation ability at 2weeks than the other implants. After 4weeks, all models had sufficiently high fixation ability in a detaching test. Bone ingrowth into the P300 implant was lower than into the other implants at 4weeks. Because of its appropriate mechanical strength, high fixation ability, and rapid bone ingrowth, our results indicate that the pore structure of the P600 implant is a suitable porous structure for orthopedic implants manufactured by SLM.

Secreted frizzled-related protein 4 is a negative regulator of peak BMD in SAMP6 mice.

We segregated a QTL for peak BMD on Chr 13 by generating congenic sublines of the senescence‐accelerated mouse SAMP6. Sfrp 4 within this locus was responsible for lower BMD of SAMP6.

Effect of indirect neural decompression through oblique lateral interbody fusion for degenerative lumbar disease.

Study Design. Prospective consecutive clinical study to assess the decompressive benefit and outcome of oblique lateral interbody fusion for lumbar degenerative diseases. Objective. To evaluate radiologically the effect of interbody distraction upon neural patency via an anterolateral retroperitoneal approach for the treatment of lumbar degenerative diseases. Summary of Background Data. Traditional treatment for symptomatic lumbar stenosis uses direct posterior decompression with or without fusion. Symptoms of radiculopathy and neurological claudication may also be alleviated indirectly through restoration of intervertebral and foraminal heights and correction of spinal alignment. Methods. Twenty-eight consecutive patients presenting with degenerative conditions that included concomitant lumbar stenosis underwent oblique lateral interbody fusion combined with percutaneous pedicle screw fixation at 52 lumbar levels without neuromonitoring. Magnetic resonance images were obtained successfully for 48 of 52 levels. The cross-sectional area of the thecal sac (CSA) was measured preoperatively and postoperatively on T2-weighted axial magnetic resonance images. Differences in CSA were compared, and the relationship between the ratio of CSA extension and that of the preoperative CSA was assessed. The change in disc height and segmental disc angle were measured. The relationships between CSA, disc height, segmental disc angle, and clinical results were assessed by correlational analysis. Results. Twenty-eight oblique lateral interbody fusions were performed successfully without neural complications. There was clinical improvement in all cases. The mean CSA increased from 99.6 mm2 preoperatively to 134.3 mm2 postoperatively (P < 0.001). The median CSA extension ratio was 30.2% and this correlated inversely with preoperative CSA. Disc height, segmental disc angle, and clinical results improved significantly. Multivariate regression analysis demonstrated that the preoperative CSA was the only independent factor that correlated inversely with the CSA extension ratio (corrected R2 = 0.361; P < 0.001). Conclusion. Spinal stenosis was resolved successfully by indirect decompression through a miniopen anterolateral retroperitoneal approach without the need for neuromonitoring. Level of Evidence: 3

Bioactivity of sol–gel-derived TiO2 coating on polyetheretherketone: In vitro and in vivo studies

UNLABELLED A polyetheretherketone (PEEK) surface was modified using a sol-gel-derived TiO2 coating in order to confer bone-bonding ability. To enhance the bonding strength of the coating layer, pretreatment with either O2 plasma or sandblasting was performed prior to sol-gel coating. Additionally, post-treatment with acid was carried out to confer apatite (calcium phosphate)-forming ability to the surface. Biomechanical and histological analyses performed using an in vivo rabbit tibia model showed that PEEK surfaces modified with sol-gel-derived TiO2 and acid post-treatment had better bone-bonding properties than uncoated PEEK surfaces. These modified surfaces also performed well in terms of their in vitro cell responses due to their modified surface chemistries and topographies. Although O2 plasma or sandblasting treatment were, for the most part, equivocal in terms of performance, we conclude that sol-gel-derived TiO2 coating followed by acid post-treatment significantly improves the bone bonding ability of PEEK surfaces, thus rendering them optimal for their use in surgical implants. STATEMENT OF SIGNIFICANCE The role of polyetheretherketone (PEEK) as an alternative biomaterial to conventional metallic implant materials has become increasingly important. However, its low bone bonding ability is yet to be resolved. This in vivo and in vitro investigation on the functionalization of PEEK surfaces highlights the utility of this material in clinical interventions that require implants, and may extend range of applications of PEEK.

Regeneration of osteonecrosis of canine scapho-lunate using bone marrow stromal cells: Possible therapeutic approach for Kienböck disease

We evaluated the ability of canine bone marrow stromal cells (cBMSCs) to regenerate bone in a cavity of the scapholunate created by curretage and freeze–thawing with liquid nitrogen (LN). Autologous BMSCs were harvested from the iliac crest and expanded in vitro. Their potential to differentiate into osteo-, chondro-, and adipogenic lineages was confirmed using a standard differentiation induction assay. LN-treated scapholunates showed no regeneration of bone tissue when the cavity was left alone, demonstrating severe collapse and deformity as observed in human Kienböck disease. A combination of β-tri-calcium phosphate and a vascularized bone graft with autologous fibroblasts failed to regenerate bone in the LN-treated cavity. When the same procedure was performed using BMSCs, however, LN-treated scapholunates showed no collapse and deformity, and the cavity was completely filled with normal cancerous bone within 4 weeks. These results suggested the potential of using BMSCs to treat Kienböck disease.

Quantitative trait locus that determines the cross-sectional shape of the femur in SAMP6 and SAMP2 mice.

We segregated a QTL on chromosome 11 that affects femoral cross‐sectional shape during growth by generating a congenic strain and an additional 16 subcongenic strains of the senescence‐accelerated mouse strain, SAMP6. The QTL region was narrowed down to a 10.0‐Mbp region.

Vertebral Endplate Cyst as a Predictor of Nonunion After Lumbar Interbody Fusion: Comparison of Titanium and Polyetheretherketone Cages

Study Design. The bone union rate after lumbar interbody fusion (LIF) using titanium (Ti) or polyetheretherketone (PEEK) cages was investigated retrospectively. Objective. To assess whether the PEEK cage is superior to the Ti cage in terms of bone union after LIF. Summary of Background Data. We previously reported that the formation of vertebral endplate cysts is useful for predicting nonunion after LIF using Ti cages. Methods. We examined 144 levels in 117 patients treated from March 2005 to July 2012 with transforaminal LIF using Ti (93 levels in 77 patients) or PEEK cages (51 levels in 40 patients) with pedicle screw fixation. Using computed tomography, vertebral endplate cyst (cyst sign) was evaluated at 3 months, and bone union status was evaluated at 1 and 2 years postoperatively. The relationship between cyst sign and union status was analyzed statistically. The bone union rate and the accuracy of the cyst sign were compared between the two groups. Results. The postoperative bone union rate was 75.2% and 74.5% at 1 year, and 82.8% and 80.4% at 2 years for Ti and PEEK groups, respectively. The rate of positive cyst sign was 17.2% and 13.7%, respectively. The nonunion rate with positive cyst sign was 100% and 100% at 1 year, and 56.2% and 71.4% at 2 years, respectively. Calculated for the cyst sign and union status, the sensitivity was 69.6% and 53.8%, and the specificity was 100% and 100%, respectively. There were no significant differences in bone union rate, rate of positive cyst sign, nonunion rate with positive cyst sign, sensitivity, and specificity between the two groups. Conclusion. The cyst sign was useful for predicting nonunion after LIF using PEEK or Ti cages. The bone union rate after LIF did not differ significantly between the two groups. Level of Evidence: 3

3-D Analysis of Pore Structure of Porous Biomaterials Using Micro Focus X-Ray Computed Tomography

Generally, characterizations of pore structures of porous biomaterials are mainly based on 2-dimensional (2-D) analysis using cross sectional micrographs. However, interconnectivity of each pore may be more important factor, when tissue ingrowth into deeper pores is considered. In this paper, using micro-CT imaging with 3-D image processing software, analyses of porous material based on 3-demensional (3-D) geometrical considerations were successfully performed. Plasmasprayed porous titanium implant (PT) and four types of sintered porous titanium implants (ST50- 200, ST50-500, ST70-200, and ST70-500) that possess different porosities (50% and 70%) and pore sizes (200-500+m and 500-1500+m) were analyzed in this study. A micro focus X-ray computed tomography system was employed to acquire microstructural information from the porous implants. Using 3-D image processing software, we performed three types of 3-D analysis including detection of the dead space (% dead pore), analysis of interconnectivity by blocking the narrow pore throat with caliber less than 52 +m (% pore with narrow throat) and analysis of material construct by contracting thin strut with thickness less than 52 +m (% construct with thin strut). ST50S and ST50L possessed interconnected porous structure with thicker strut; however, pore throat was considered to be relatively narrow. On the other hand, PT implant possesses favorable interconnectivity despite its’ low porosity; however, relatively thin strut indicate the structural disadvantage for mechanical property. These results suggest that the 3-D analysis of pore and strut structure using micro focus X-ray computed tomography and 3-D image processing software will provide effective information to develop porous implant.