Yasuyuki Shiozaki

A novel, visible light-induced, rapidly cross-linkable gelatin scaffold for osteochondral tissue engineering

Osteochondral injuries remain difficult to repair. We developed a novel photo-cross-linkable furfurylamine-conjugated gelatin (gelatin-FA). Gelatin-FA was rapidly cross-linked by visible light with Rose Bengal, a light sensitizer, and was kept gelled for 3 weeks submerged in saline at 37°C. When bone marrow-derived stromal cells (BMSCs) were suspended in gelatin-FA with 0.05% Rose Bengal, approximately 87% of the cells were viable in the hydrogel at 24 h after photo-cross-linking, and the chondrogenic differentiation of BMSCs was maintained for up to 3 weeks. BMP4 fusion protein with a collagen binding domain (CBD) was retained in the hydrogels at higher levels than unmodified BMP4. Gelatin-FA was subsequently employed as a scaffold for BMSCs and CBD-BMP4 in a rabbit osteochondral defect model. In both cases, the defect was repaired with articular cartilage-like tissue and regenerated subchondral bone. This novel, photo-cross-linkable gelatin appears to be a promising scaffold for the treatment of osteochondral injury.

Enhanced in vivo osteogenesis by nanocarrier-fused bone morphogenetic protein-4

Purpose Bone defects and nonunions are major clinical skeletal problems. Growth factors are commonly used to promote bone regeneration; however, the clinical impact is limited because the factors do not last long at a given site. The introduction of tissue engineering aimed to deter the diffusion of these factors is a promising therapeutic strategy. The purpose of the present study was to evaluate the in vivo osteogenic capability of an engineered bone morphogenetic protein-4 (BMP4) fusion protein. Methods BMP4 was fused with a nanosized carrier, collagen-binding domain (CBD), derived from fibronectin. The stability of the CBD-BMP4 fusion protein was examined in vitro and in vivo. Osteogenic effects of CBD-BMP4 were evaluated by computer tomography after intramedullary injection without a collagen–sponge scaffold. Recombinant BMP-4, CBD, or vehicle were used as controls. Expressions of bone-related genes and growth factors were compared among the groups. Osteogenesis induced by CBD-BMP4, BMP4, and CBD was also assessed in a bone-defect model. Results In vitro, CBD-BMP4 was retained in a collagen gel for at least 7 days while BMP4 alone was released within 3 hours. In vivo, CBD-BMP4 remained at the given site for at least 2 weeks, both with or without a collagen–sponge scaffold, while BMP4 disappeared from the site within 3 days after injection. CBD-BMP4 induced better bone formation than BMP4 did alone, CBD alone, and vehicle after the intramedullary injection into the mouse femur. Bone-related genes and growth factors were expressed at higher levels in CBD-BMP4-treated mice than in all other groups, including BMP4-treated mice. Finally, CBD-BMP4 potentiated more bone formation than did controls, including BMP4 alone, when applied to cranial bone defects without a collagen scaffold. Conclusion Altogether, nanocarrier-CBD enhanced the retention of BMP4 in the bone, thereby promoting augmented osteogenic responses in the absence of a scaffold. These results suggest that CBD-BMP4 may be clinically useful in facilitating bone formation.

Bone engineering by phosphorylated-pullulan and β-TCP composite

A multifunctional biomaterial with the capacity bond to hard tissues, such as bones and teeth, is a real need for medical and dental applications in tissue engineering and regenerative medicine. Recently, we created phosphorylated-pullulan (PPL), capable of binding to hydroxyapatite in bones and teeth. In the present study, we employed PPL as a novel biocompatible material for bone engineering. First, an in vitro evaluation of the mechanical properties of PPL demonstrated both PPL and PPL/β-TCP composites have higher shear bond strength than materials in current clinical use, including polymethylmethacrylate (PMMA) cement and α-tricalcium phosphate (TCP) cement, Biopex-R. Further, the compressive strength of PPL/β-TCP composite was significantly higher than Biopex-R. Next, in vivo osteoconductivity of PPL/β-TCP composite was investigated in a murine intramedular injection model. Bone formation was observed 5 weeks after injection of PPL/β-TCP composite, which was even more evident at 8 weeks; whereas, no bone formation was detected after injection of PPL alone. We then applied PPL/β-TCP composite to a rabbit ulnar bone defect model and observed bone formation comparable to that induced by Biopex-R. Implantation of PPL/β-TCP composite induced new bone formation at 4 weeks, which was remarkably evident at 8 weeks. In contrast, Biopex-R remained isolated from the surrounding bone at 8 weeks. In a pig vertebral bone defect model, defects treated with PPL/β-TCP composite were almost completely replaced by new bone; whereas, PPL alone failed to induce bone formation. Collectively, our results suggest PPL/β-TCP composite may be useful for bone engineering.

Vertebral rotation during pedicle screw insertion in patients with cervical injury

BackgroundCervical pedicle screws, when misplaced, tend to perforate laterally. One of the reasons for lateral perforation is vertebral rotation during screw insertion. However, actual vertebral rotation during pedicle screw insertion is unknown. In this study, we measured vertebral rotation during pedicle screw insertion in patients with cervical injury.MethodsWe inserted 76 pedicle screws into 38 vertebrae (C2 to C7) in 17 patients. All patients had some type of cervical injury. Screws were placed using intraoperative acquisition of data acquired with the isocentric C-arm fluoroscope (Iso-C3D) and computer navigation. We made screw holes using an image-guided awl, and we took images of cervical vertebrae in the neutral and rotational positions using navigation. Images of 76 insertions and rotational positions were taken while each cervical vertebra was under maximum stress at the time we were making the pedicle hole by awl.ResultsAverage cervical vertebra rotation was 10.6° (range 6 to 17) at C2, 9.1° (5 to 13) at C3, 7.8° (6 to 9) at C4, 6.7° (4 to 11) at C5, 4.9° (2 to 8) at C6, and 2.8° (0 to 4) at C7. Vertebrae in the upper and middle cervical spine rotated more than the lower cervical spine vertebrae. Of the 76 pedicle screws inserted into vertebrae between C2 and C7, 74 screws (97.4%) were classified as grade 1 (no pedicle perforation).ConclusionsIn this study, upper and middle cervical vertebrae in patients with neck injuries rotated more than the lower vertebrae. We should be especially careful of cervical rotation during screw insertion from C2 to C6, so as to prevent vertebral artery injury.

Collagen-Binding Hepatocyte Growth Factor (HGF) alone or with a Gelatin-furfurylamine Hydrogel Enhances Functional Recovery in Mice after Spinal Cord Injury

The treatment of spinal cord injury (SCI) is currently a significant challenge. Hepatocyte growth factor (HGF) is a multipotent neurotrophic and neuroregenerative factor that can be beneficial for the treatment of SCI. However, immobilized HGF targeted to extracellular matrix may be more effective than diffusible, unmodified HGF. In this study, we evaluated the neurorestorative effects of an engineered HGF with a collagen biding domain (CBD-HGF). CBD-HGF remained in the spinal cord for 7 days after a single administration, while unmodified HGF was barely seen at 1 day. When a gelatin-furfurylamine (FA) hydrogel was applied on damaged spinal cord as a scaffold, CBD-HGF was retained in gelatin-FA hydrogel for 7 days, whereas HGF had faded by 1 day. A single administration of CBD-HGF enhanced recovery from spinal cord compression injury compared with HGF, as determined by motor recovery, and electrophysiological and immunohistochemical analyses. CBD-HGF alone failed to improve recovery from a complete transection injury, however CBD-HGF combined with gelatin-FA hydrogel promoted endogenous repair and recovery more effectively than HGF with hydrogel. These results suggest that engineered CBD-HGF has superior therapeutic effects than naïve HGF. CBD-HGF combined with hydrogel scaffold may be promising for the treatment of serious SCI.

Motion Induced Artifact Mimicking Cervical Dens Fracture on the CT Scan: A Case Report

The diagnostic performance of helical computed tomography (CT) is excellent. However, some artifacts have been reported, such as motion, beam hardening and scatter artifacts. We herein report a case of motion-induced artifact mimicking cervical dens fracture. A 60-year-old man was involved in a motorcycle accident that resulted in cervical spinal cord injury and quadri plegia. Reconstructed CT images of the cervical spine showed a dens fracture. We assessed axial CT in detail, and motion artifact was detected.

Relationship between Displacement of the Psoas Major Muscle and Spinal Alignment in Patients with Adult Spinal Deformity

Study Design Cross sectional study. Purpose To clarify the difference in position of the psoas muscle between adult spinal deformity (ASD) and lumbar spinal stenosis (LSS). Overview of Literature Although it is known that the psoas major muscle deviates in ASD patients, no report is available regarding the difference in comparison with LSS patients. Methods This study investigates 39 patients. For evaluating spinal alignment, pelvic tilt (PT), pelvic incidence (PI), sacral slope, lumbar lordosis (LL), PI–LL, Cobb angle, and the convex side, the lumbar curves were measured. For measuring the position of the psoas major at the L4/5 disk level, magnetic resonance imaging was used. The displacements of psoas major muscle were measured separately in the anterior–posterior and lateral directions. We examined the relationship between the radiographic parameters and anterior displacement (AD) and lateral displacement (LD) of the psoas major muscle. Results AD was demonstrated in 15 cases with ASD and nine cases with LSS (p>0.05). LD was observed in 13 cases with ASD and no cases with LSS (p<0.01). The Cobb angle was significantly greater in cases with AD than in those without AD (p=0.04). PT, LL, PI–LL, and Cobb angle were significantly greater in cases with LD (p<0.05). All cases with LD had AD, but no case without AD had LD (p<0.001). The side of greater displacement at L4/5 and the convex side of the lumbar curve were consistent in all cases. Conclusions Despite AD being observed in LSS as well, LD was observed only in the ASD group. Radiographic parameters were worse when LD was seen, rather than AD.