Biomedical subjects

William W Lu

Publications and source records attributed to William W Lu.

At least 19 recordsLinked to original sources

PubMed2006

Mechanical testing of a smart spinal implant locking mechanism based on nickel-titanium alloy.

STUDY DESIGN: Development and testing of a new spinal implant-locking mechanism based on the special properties of nickel-titanium alloy. OBJECTIVE: To develop a new self-tightening locking mechanism to reduce fretting corrosion at implant junctions. SUMMARY OF BACKGROUND DATA: All current implant locking involves tightening of a nut against the rod and screw head to form a coupling. Particulate debris is generated, and the coupling becomes loose because of wear between the rod and locking mechanism (fretting). To avoid this fretting, a new locking mechanism with an automatic retightening effect based on the superelastic and shape-memory properties of nickel-titanium alloy has been developed. METHOD: The new coupling made of nickel-titanium alloy will tightly lock the rod when temperature increases to 50 degrees C (shape-memory effect). If fretting occurs, the coupling will further tighten itself around the rod (superelastic effect). This new coupling is mechanically tested against 4 current implant couplings. RESULTS: In axial compression, conventional couplings failed between 570 and 740 N, while the new coupling reached 800 N without loosening. In axial rotation, conventional devices failed between 1.8 and 5.3 Nm, while the new coupling reached 6.5 Nm without failure. During testing, the retightening effect could be seen on the force versus displacement plot. CONCLUSIONS: To our knowledge, the self-tightening coupling is a new concept not previously described and is attributable to the superior superelastic effect of the new coupling. This implant coupling has the potential to be used as a very low profile system and also in nonfusion technologies in which demands on the coupling would not higher without the protection of spinal fusion.

Alloys↗

PubMed2006

Insulin-like growth factor-1 treatment prevents anti-Fas antibody-induced apoptosis in endplate chondrocytes.

STUDY DESIGN: In vitro investigation of vertebral endplate chondrocyte apoptosis. OBJECTIVES: To determine whether Fas antibody caused apoptosis in endplate chondrocytes, and whether insulin-like growth factor-1 (IGF-1) inhibited this effect. Integrin-alpha1 and focal adhesion kinase (FAK) expression in conjunction with apoptosis was also investigated. SUMMARY OF BACKGROUND DATA: Binding of Fas antibody to Fas mimics Fas-FasL ligation, which causes apoptosis. IGF-1 has been shown to have anti-apoptotic effects. MATERIALS AND METHODS: Rat cervical endplate chondrocytes were cultured and treated with Fas antibody, with or without IGF-1. Cellular morphology was examined by microscopy. Apoptotic changes were evaluated by transmission electron microscopy, TUNEL staining, and immunostaining. Apoptosis-induced changes in the expression of integrin-alpha1 chain and FAK were also investigated. RESULTS: Endplate chondrocytes were able to be cultured; a chondrocytic phenotype was maintained. Fas antibody induced apoptosis in endplate chondrocytes; this was confirmed by TUNEL staining. Bcl-2 expression was decreased by Fas antibody, while Bax expression increased. Integrin-alpha1 and FAK expression was decreased by Fas antibody. IGF-1 treatment inhibited these Fas antibody-induced changes. CONCLUSIONS: Fas antibody induces apoptosis and decreases Integrin-alpha1 and FAK expression in cultured endplate chondrocytes; IGF-1 is protective against these changes.

Animals↗

PubMed2006

Consequence of paraspinal muscle after spinal fusion: an experimental study.

Posterior lumbar spinal fusion is a common surgery of spine. The parapsinal muscular dysfunction was postulated to be due to injured paraspinal muscle inflicted by the surgery. To better understand the muscle dysfunction after spinal fusion, this descriptive study evaluated electrophysiology and histology changes in paraspinal muscle of rabbits with and without fusion. Three New Zealand white rabbits underwent 2-level posterior spinal fusion with instrumentation. Anothor 3 rabbits underwent surgical exposure alone and served as sham control. Pre-operative and follow-up electromyography (EMG) and histological assessment were performed in a 6-month interval. All fusion achieved solid union judged by post-mortem examination. Root mean square (RMS) of EMG showed decrease in both fusion and control group immediately after surgery, but the control group recovered to pre-operative value at 6 months follow-up. At 6 months after operation, the fusion group showed lower RMS in fused region than adjacent region. In term of median frequency (MF) changes, the control group did not show obvious difference between pre- and post-operative period. However, fusion group showed obvious decrease of MF in fusion region, but increase in lower adjacent region. Histology reviewed fatty infiltration in fusion region at 6 months after spinal fusion. In addition, the muscle fiber size presented smaller in fusion region than that of pre-operative status. These results would demonstrate the lower activities and muscle disuse atrophy of paraspinal muscles in the fusion region. While, higher muscular activities were found in the lower adjacent region, which may indicate muscle hypertrophy.

Animals↗

PubMed2005

Effects of hydroxyapatite in 3-D chitosan-gelatin polymer network on human mesenchymal stem cell construct development.

Human mesenchymal stem cells (hMSCs) have great potential in bone tissue engineering, and hydroxyapatite (HA), a natural component of human hard tissues, is believed to support hMSC growth and osteogenic differentiation. In this study, two types of biomimetic composite materials, chitosan-gelatin (CG) and hydroxyapatite/chitosan-gelatin (HCG), were fabricated and compared to examine the effects of HA on hMSC adhesion and 3-D construct development. The 2-D membranes were prepared to examine the influence of HA on adhesion efficiency of hMSCs, while 3-D porous scaffolds were produced to investigate the effects of HA on material adsorption properties and 3-D hMSC construct development. HA was found to promote protein and calcium ion adsorption of the 3-D porous scaffolds in the complete tissue culture media. HMSCs exhibited higher initial cell adhesion efficiency to 2-D HCG membranes, and maintained higher proliferation rates in the 3-D porous HCG than CG scaffolds with 3.3 times higher final DNA amount in HCG scaffolds over a 35-day period. Colony forming unit-fibroblast (CFU-F) assays showed that higher percentages of cells maintained their progenicity in the 3-D porous HCG scaffolds over the 35-day culture period. Differentiation assays indicated that the multi-lineage differentiation potential of the hMSCs was preserved in both 3-D porous scaffolds. However, higher alkaline phosphate activity was detected in the 3-D porous HCG scaffolds upon osteogenic induction indicating improved osteogenic differentiation potential. The results demonstrate that enhanced protein and calcium ion adsorption properties of HA in the CG polymer network improve initial cell adhesion and long-term growth, favor osteogenic differentiation upon induction, as well as maintain the progenicity of the 3-D hMSC constructs.

Bone Substitutes↗

PubMed2005

Vertebroplasty by use of a strontium-containing bioactive bone cement.

STUDY DESIGN: A review of the laboratory and clinical data for a new strontium-containing hydroxyapatite bioactive bone cement. OBJECTIVES: To compare the properties of the strontium-containing bioactive bone cement with those of polymethyl methacrylate (PMMA) and hydroxyapatite (HA) bone cements. SUMMARY OF BACKGROUND DATA: Vertebroplasty and kyphoplasty using conventional PMMA bone cements have been effectively used to treat osteoporotic spine fractures with good short- and medium-term results. However, PMMA has some undesirable properties, including its high setting temperature, lack of osseointegration, and large stiffness mismatch with osteoporotic bone. These properties are responsible for some postoperative complications. METHODS: Strontium-containing hydroxyapatite (Sr-HA) bioactive bone cement consists of a filler blend of strontium-containing hydroxyapatite, fumed silica and benzoyl peroxide; and a resin blend of bisphenol A diglycidylether methacrylate, triethylene glycol dimethacrylate, poly(ethylene glycol) methacrylate, and N, N-dimethyl-p-toluidine. Its properties, including mechanical strength, setting temperature, biocompatibility, and osseoinduction, were compared with other cements in vitro and in vivo. Early clinical results are presented. RESULTS: The Sr-HA cement has a setting time of 15 to 18 minutes, a maximum setting temperature of 58 degrees C, a compressive strength of 40.9 MPa, bending strength of 31.3 MPa, and a bending modulus of 1,408 MPa. The bending strength and modulus are closer to human cancellous bone. Sr-HA cement promotes osteoblast attachment and mineralization in vitro and bone growth and osseointegration in vivo. In a pilot study, 23 cases of osteoporotic fractures treated with this cement with a mean follow-up of 18 months suggest that it is as effective as PMMA in relieving pain. DISCUSSIONS: Oral strontium has been shown to induce new bone formation and is effective in reducing fracture risk in osteoporosis. Our data suggest that strontium delivered locally has the same effect; thus, the combination of strontium with HA in a cement with a low setting temperature, adequate stiffness, and low viscosity makes this a good bioactive cement for vertebroplasty and kyphoplasty.

Animals↗

PubMed2005

A new operative classification of idiopathic scoliosis: a peking union medical college method.

STUDY DESIGN: A retrospective radiographic study on the type of surgically treated idiopathic scoliosis, with a prospective study on the reliability of the type-related fusion guide. OBJECTIVES: To identify and classify surgically treated idiopathic scoliosis, and define its related fusion levels by a new classification system. SUMMARY OF BACKGROUND DATA: Some classification methods for idiopathic scoliosis have been suggested. However, poor intraobserver reproducibility and interobserver reliability were experienced in these studies, and were not appropriate for guiding surgical planning. METHODS: A total of 427 surgically treated idiopathic scoliosis cases were reviewed. Preoperative and postoperative standing anteroposterior, lateral, and preoperative supine side-bending radiograph were analyzed using the Scoliosis Research Society definition of scoliosis and curve apex. The resulting classification was tested for intraobserver reliability and interobserver reliability, and by 6 surgeons. Apical frequencies were determined for each type, and prospective surgical testing of the new type and its related fusion guide was performed. RESULTS: Three major types and 13 subtypes were identified, of which the Peking Union Medical College type I accounted for 56.62%, type II 42.16%, and type III 1.22%. The interobserver reliability testing was 85% (kappa coefficient 0.832), while intraobserver reproducibility was 91% (kappa coefficient 0.898). Each type had its corresponding fusion levels. A prospective study of 152 cases was performed according to the classification. All of these cases were followed over 18 months, and no postoperative decompensation was noted. CONCLUSION: The Peking Union Medical College classification of idiopathic scoliosis is one system to combine each type with its corresponding fusion level, and it had much higher interobserver reliability and intraobserver reproducibility than the King system. Further prospectivestudies would help to clarify and expand this system.

Adolescent↗

PubMed2005

Pure shear properties of lumbar spinal joints and the effect of tissue sectioning on load sharing.

STUDY DESIGN: An in vitro biomechanical study on lumbar intervertebral joints. OBJECTIVES: To examine the mechanical properties of lumbar motion segments under pure shear loading and establish whether a simple model for functional differentiation between the anterior column and the posterior elements is applicable. SUMMARY OF BACKGROUND DATA: Anteroposterior shear has been implicated as a major factor in spinal instability. There is a substantial amount of data on shear motion as a coupled part of flexion-extension; data on the pure shear properties of intervertebral joints is limited. METHODS: Eighteen human cadaver lumbar motion segments were subject to nondestructive testing under pure shear loads (anterior shear and posterior shear). An MTS standard testing machine was used to record the load-deformation characteristics of specimens subject to deformation at a constant rate to a maximum shear load of approximately 250 N. Tissue sectioning was then performed with the specimen mounted in the testing machine. Eight specimens were sectioned through the intervertebral disc, including the anterior and posterior longitudinal ligaments, and 8 specimens were sectioned through the pedicles to remove the posterior elements. The same deformation pattern applied to the intact specimen was then reapplied to the sectioned specimen, and the load-deformation characteristics following sectioning were evaluated. RESULTS: The shear stiffness of the intact segments were found to be higher in anterior shear (mean group A = 583.8, B = 607 N/mm) than in posterior shear (mean group A = 469, B = 438.4 N/mm). Section of the anterior column and adjacent longitudinal ligaments resulted in a mean stiffness decreased by 22.8% of the intact value under anterior shear and 23.9% under posterior shear. Much larger change in shear stiffness was seen, and the mean sectioned stiffness dropped by 77.7% in anterior shear and 79% in posterior shear after removal of the posterior elements. After the anterior column was sectioned, 12% and 18% increases in the deformation for anterior and posterior directions were seen, whereas a distinct increase in the deformations was found after posterior elements sectioned. CONCLUSIONS: The posterior elements of the lumbar spine are more efficient in resisting anterior and posterior shear loads. However, the anterior column will exhibit similar load-displacement characteristics if subject to greater deformations. The sum of the normalized mean shear loads of the anterior column and posterior elements sustained at maximum intact deformation is significantly different from the shear load sustained by the intact spine at the same deformation. A simple concept of load sharing between the anterior column and the posterior elements may not be valid.

Adult↗

PubMed2005

Effect of segmental artery ligation on the blood supply of the thoracic spinal cord during anterior spinal surgery: a quantitative histomorphological fresh cadaver study.

STUDY DESIGN: Human cadaver quantitative morphometric analysis of the blood vessels in the spinal cord after ligation of segmental arteries. OBJECTIVES: To investigate the effect of ligation of segmental arteries on the quantity and density of the blood vessels in the spinal cord. SUMMARY OF BACKGROUND DATA: Ligation of segmental arteries is often used in the anterior approach for correction scoliosis. However, whether or not segmental artery ligation is liable to deny the spinal cord an adequate blood supply, thus leading to paraplegia, still remains controversial. METHODS: Eleven fresh cadavers were divided into control, unilateral, and bilateral groups. For the unilateral and bilateral groups, 5 segmental vertebral arteries (T7-T11) were ligated unilaterally and bilaterally, respectively. Then, the number and density of blood vessels at different levels in the 3 groups were measured. RESULTS: Compared to that of the corresponding level in the control group, the number of blood vessels at T5 to L1 all decreased in the ligation groups. And significant differences were found at T8 (82.80 +/- 16.36), T10 (77.80 +/- 19.80), and T11 (99.20 +/- 14.85) levels, compared to those of the corresponding levels in the control group: T8 (175.80 +/- 8. 31), T9 (176.40 +/- 32. 33), T10 (171.40 +/- 9. 73), and T11 (189.20 +/- 15. 92). Further decrease was found at each corresponding level in the bilateral group, and significant differences were found at T8 (65.80 +/- 15.55), T9 (24.80 +/- 13.43), T10 (0), T11 (0), and T12 (0) levels. Similar results were obtained with regard to the density of blood vessels. Significant differences were found at T11 (1.246 +/- 0.112) and L1 (1.349 +/- 0.109) in the unilateral group, and T9 (0.260 +/- 0.088), T10 (0), T11 (0), T12 (0), and L1 (0.147 +/- 0.117) in the bilateral group compared to those of the corresponding levels in the control group: T9 (1.810 +/- 0.202), T10 (1.833 +/- 0.175), T11 (2.308 +/- 0.335), T12 (2.510 +/- 0.617), and L1 (2.193 +/- 0.033). CONCLUSIONS: This study suggests that the more levels the ligation encompasses, the higher the risk of spinal cord damage. Therefore, caution should be taken when several segmental arteries are to be ligated in the clinical setting. What is more, bilateral ligation, which is worse than unilateral ligation, can lead to a significant decrease in the number and density of blood vessels of the spinal.

Adolescent↗

PubMed2005

A stronger bicortical sacral pedicle screw fixation through the s1 endplate: an in vitro cyclic loading and pull-out force evaluation.

STUDY DESIGN: The insertion torque and pull-out force after cyclic loading of the bicortical sacral pedicle screw through the S1 endplate were tested using human cadaveric specimens. OBJECTIVES: The purpose of this study was to (1) evaluate the effect of cyclic loading on the pull-out force of two different techniques of bicortical sacral pedicle screw fixation and (2) to correlate the pull-out force after cyclic loading with the screw insertion torque. SUMMARY OF BACKGROUND DATA: Biomechanical studies using conventional sacral pedicle screw fixation techniques have demonstrated reduction in stiffness and strength after cyclic loading. Technical difficulties with anterior sacral cortex penetration and frequent screw loosening have been reported in clinical studies. In the authors' center, a new method of sacral pedicle screw fixation bicortically through the S1 endplate has been used successfully in the clinical setting. However, the mechanical stability of this new technique after undergoing cyclic loading has not been documented in the literature. METHODS: Seven-millimeter compact Cotrel-Dubousset sacral screws were randomly assigned by side (left vs. right) and inserted bicortically either anteromedially through the anterior sacral cortex or superiorly through the S1 endplate of 17 fresh frozen human sacrum. The tk;4maximum insertion torque for each screw was measured. Cyclic loading from 40 N to 400 N was applied to each screw at a frequency of 2 Hz for 20,000 cycles. Pull-out tests were conducted after completion of the cyclic tests. RESULTS: The mean maximum insertion torque and mean pull-out force following cyclic loading were significantly higher for bicortical fixation through the S1 endplate (mean 3.17 N.m and 1457 N) than bicortical fixation through the anterior sacral cortex (mean 1.98 N.m and 1122 N). Both S1 endplate and anterior cortical fixation techniques demonstrated significant correlations between insertion torque and pull-out force following cyclic loading. CONCLUSIONS: In sacral pedicle screw fixation, screw trajectory through the S1 endplate was significantly stronger than screws penetrating the anterior sacral cortex. Insertion torque was a good intraoperative indicator of screw pull-out force after cyclic loading.

Adult↗

PubMed2005

An investigation on the physicochemical properties of chitosan/DNA polyelectrolyte complexes.

In this work, to eliminate the effect of the hydrophobicity of N-acetyl groups in chitosan on the interaction between chitosan and DNA, a water soluble chitosan with molecular weight of 5000 and deacetylated degree of 99% was selected to complex with DNA at varied charged ratios. The physicochemical properties of chitoplexes were investigated by means of FTIR, circular dichroism (CD), static fluorescence spectroscopy, and atomic force microscopy (AFM). The results indicated that upon interacting with chitosan, the DNA molecules saved a B conformation, and the binding affinity of chitosan to DNA was dependent on pH of media. At pH 5.5, highly charged chitosan had a strong binding affinity with DNA; whereas in pH 12.0 medium, only weak interactions existed. The CD spectra of Hoechst 33258 competitive displacement revealed that chitosan was partially bound to the minor groove of DNA. The morphology of chitosan/DNA complexes was strongly dependent upon the charge ratios. At charge ratio (+/-) of 1:4, not all DNA could be entrapped in the complex; at ratio of 8:1, the spherical complexes with mean size of nanoscale were formed without free DNA, but no typical toroid patterns were observed, which might stem from the strong compact of DNA caused by highly charged chitosan. It was supposed that the strong interaction of chitosan with DNA possibly prevented gene unpacking from chitosan vector, consequently restraining gene expression in nucleus.

Chitosan↗

PubMed2005

Multi-adaptive filtering technique for surface somatosensory evoked potentials processing.

Somatosensory evoked potential (SEP) testing has been widely applied to diagnosis of various neurological disorders. However, SEP recorded using surface electrodes is buried in noises, which makes the signal-to-noise ratio (SNR) very poor. Conventional averaging method usually requires up to thousands of raw SEP input trials to increase the SNR so that an identifiable waveform can be produced for latency and amplitude measurement. In this study, a multi-adaptive filtering (MAF) technique, emerging from the combination of well-developed adaptive noise canceller and adaptive signal enhancer, is introduced for fast and accurate surface SEP extraction. The MAF technique first processes the raw surface recorded SEP by the Canceller with a reference noise channel of background noise for adaptive subtraction before entering the Enhancer. The MAF was verified by filtering simulated SEP signals in which electroencephalography and Gaussian noise of different SNRs were added. It was found that the MAF could effectively suppress the noise and enhance the SEP components such that the SNR of the SEP is improved. Results showed that MAF with 50 input trials could provide similar performance in SEP detection to those extracted by the conventional averaging method with 1000 trials even at an SNR of -20 dB.

Algorithms↗

PubMed2005

[Biomechanical evaluation of stiffness of long-segment instrumented spine].

OBJECTIVE: To test the changes of the stiffness of the intact, released, and instrumented spines in an in vitro porcine model. METHODS: Twelve porcine spines (12 segments each) were harvested for the biomechanical tests with Material Test System. Stiffness during flexion, extension, lateral bending, and axial rotation were recorded; then the specimen was released with intervertebral discs and the facet joints removed, followed by repeating the biomechanical tests for stiffness; and finally, a double-rod titanium construct was applied for internal fixation to each released spine and stiffness tests were repeated again. RESULTS: Compared with the intact porcine spines [stiffness during flexion, extension, lateral bending, and axial rotation was 52.89 +/- 15.98, 105.43 +/- 56.38, 42.09 +/- 14.73, and (16.94 +/- 4.85) N x mm/degrees, respectively], the stiffness of the released porcine spines [stiffness during flexion, extension, lateral bending, and axial rotation was 44.04 +/- 13.73, 41.46 +/- 10.80, 31.75 +/- 7.23, and (9.10 +/- 2.07)N x mm/degrees, respectively] significantly decreased (P < 0.05), while significantly increased stiffness was found in the instrumented porcine spines [stiffness during flexion, extension, lateral bending, and axial rotation was 385.96 +/- 143.25, 138.96 +/- 59.41, 152.56 +/- 87.15, and (55.91 +/- 16.49) N x mm/degrees, respectively] (P < 0.05). CONCLUSION: Higher instant stiffness was found in instrumented spine than the intact one during flexion, extension, lateral bending and axial rotation.

Animals↗

PubMed2004

Combination of adeno-associated virus and adenovirus vectors expressing bone morphogenetic protein-2 produces enhanced osteogenic activity in immunocompetent rats.

We have previously shown that gene therapy using adeno-associated virus (AAV) carrying bone morphogenetic proteins (BMPs) is a promising strategy for new bone formation in vivo in SD rats. However, it had a relatively low transduction efficiency. We investigate here whether enhanced osteogenic activity can be achieved without eliciting a severe immune response, using a cocktail of AAV-BMP2 and adenovirus (Ad)-BMP2 as a vector system. The muscles of SD rats were injected with either AAV-BMP2, Ad-BMP2, or an AAV-BMP2/Ad-BMP2 cocktail, and the in vivo bone formation was determined at eight weeks post-injection. Radiographic examination demonstrated that the addition of a low level of Ad-BMP2 to AAV-BMP2 produced significantly higher new bone formation than the use of AAV-BMP2 alone. Histological and immunohistological analysis revealed an enlarged bone-forming area and a long-term BMP2 expression, without pronounced infiltration of lymphocytes. Our results provide the first evidence that the introduction of a low level of adenovirus in vivo in immunocompetent subjects can greatly enhance AAV-mediated gene transfer, without inducing severe immune responses. This cocktail vector system may offer an attractive way of improving the efficiency of AAV-based gene delivery.

Adenoviridae↗

PubMed2004

A rapid temperature-responsive sol-gel reversible poly(N-isopropylacrylamide)-g-methylcellulose copolymer hydrogel.

Poly(N-isopropylacrylamide) (PNIPAAm) was grafted to methylcellulose (MC) with various feeding ratios using ammonium persulfate and N,N,N',N'-tetramethyl ethylene diamine as an initiator. FTIR results confirm the formation of PNIPAAm-g-MC copolymers. The temperature responsiveness of copolymer gels was investigated by turbidimetry, dynamic contact angle (DCA), differential scanning calorimetry and dynamic mechanical analysis (DMA). The results indicate that PNIPAAm-g-MC hydrogels are strongly temperature responsive. At lower contents of MC, the lower critical solution temperature (LCST) is decreased, whereas further increasing MC contents raises the LCSTs. It is observed that the phase transition of the hydrogels occurs reversibly within 1 min, and near body temperature, a rigid gel can be generated in a certain range of MC content. What is more, the incorporation of MC prevents the syneresis of copolymer hydrogel. DMA measurement reveals that the storage moduli (E') of the gels increase upon increasing MC contents, and moreover the values of E' go up markedly above LCST. The copolymer hydrogels hold a promise as a blood vessel barrier by tuning gelation temperature, gelation time and mechanical strength.

Acrylic Resins↗

PubMed2003

Adeno-associated virus-mediated bone morphogenetic protein-4 gene therapy for in vivo bone formation.

Adeno-associated virus (AAV) is so far the most valuable vehicle for gene therapy because it has no association with immune response and human disease. The present study was conducted to investigate the feasibility of AAV-mediated BMP4 gene transfer for bone formation. In vitro study suggested that AAV-BMP4 vectors could transduce myoblast C2C12 cells and produce osteogenic BMP4. In vivo study demonstrated that new bone formation could be induced by direct injection of AAV-BMP4 into the skeletal muscle of immunocompetent rats. Histological analysis revealed that the newly formed bone was induced through endochondral mechanism. Immunohistochemical staining further demonstrated that AAV-BMP4 gene delivery could mediate long-term transduction, and the involvement of BMP4 expression was responsible for the endochondral ossification. This study is, to our knowledge, the first report in the field of AAV-based BMP gene transfer and should be promising for clinical orthopaedic applications.

Animals↗

PubMed2002

In vivo new bone formation by direct transfer of adenoviral-mediated bone morphogenetic protein-4 gene.

Previous studies have demonstrated that bone morphogenetic protein-4 (BMP4) could participate in vivo endochondral ossification and is one of the main local contributing factors in the early stage of fracture healing. To investigate the effectiveness of BMP4 gene transfer, we constructed an adenoviral vector, Ad-BMP4, and evaluated its osteoinduction activity both in vitro and in vivo. In vitro study suggested that this vector could efficiently transduce mouse myoblast C2C12 cells and produce osteogenic BMP4 protein, as confirmed by immunofluorescence analysis and alkaline phosphatase activity assay. For in vivo study, Ad-BMP4 was directly injected into the hind limb muscles of male athymic nude rats. Visible new bone formation under X-ray films could be detected as early as three weeks post-injection. The bone tissue was further analyzed by histological staining and revealed a typical remodeled bone structure. In conclusion, this study is the first to establish the feasibility of adenovirus-based BMP4 gene therapy for bone regeneration.

Adenoviridae↗

PubMed2002

Paraspinal muscle activities of patients with scoliosis after spine fusion: an electromyographic study.

STUDY DESIGN: This prospective study compared the electromyographic activities of paraspinal muscles between normal subjects and patients with scoliosis before and after spine fusion. OBJECTIVE: To investigate the functional changes of paraspinal muscles before and after spine fusion using surface electromyography. SUMMARY OF BACKGROUND DATA: Idiopathic scoliosis is a common spine deformity. Surgical correction followed by spine fusion is the basic method of treatment, but the functional changes in paraspinal muscles after spine fusion still are unknown. METHODS: For this study, 15 healthy subjects and 19 patients with idiopathic scoliosis were recruited. All 19 patients received posterior spine fusion from T2 to T5 to T12. The surface electromyography for normal subjects and for patients before and after spine fusion was recorded bilaterally along the thoracic and lumbar paraspinal muscles for different postures. Root mean square and median frequency values of electromyographic activities were used to compare results between normal subjects and patients with scoliosis before and after spine fusion. RESULTS: Electromyographic activities showed significant differences between normal control subjects and patients with pre- or postoperative scoliosis. After spine fusion, electromyography showed lower root mean square activity in the thoracic region and higher root mean square activity in the lumbar region. Patients with preoperative scoliosis showed lower median frequency in the thoracic region and higher median frequency in the lumbar region than normal subjects and patients with postoperative scoliosis. The group with preoperative scoliosis showed the least symmetrical paraspinal muscle activity, followed by the postoperative and normal groups. CONCLUSIONS: Patients with scoliosis present unbalanced electromyographic activity in the paravertebral muscles, which is diminished by spine fusion, but does not return to the values found in normal subjects. The paraspinal muscles in the thoracic region showed lower activity after spine fusion, probably because of atrophy. Higher muscular activity was found in the lumbar region, which may lead to muscle hypertrophy.

Adolescent↗

PubMed2002

Preparation and histological evaluation of biomimetic three-dimensional hydroxyapatite/chitosan-gelatin network composite scaffolds.

A novel biodegradable hydroxyapatite/chitosan-gelatin network (HA/CS-Gel) composite of similar composition to that of normal human bone was prepared as a three-dimensional biomimetic scaffold by phase separation method for bone tissue engineering. Changing the solid content and the compositional variables of the original mixtures allowed control of the porosities and densities of the scaffolds. The HA granules were dispersed uniformly in the organic network with intimate interface contact via pulverizing and ultrasonically treating commercial available HA particles. Scaffolds of 90.6% porosity were used to examine the proliferation and functions of the cells in this three-dimensional microenvironment by culturing neonatal rat caldaria osteoblasts. Histological and immunohistochemical staining and scanning electron microscopy observation indicated that the osteoblasts attached to and proliferated on the scaffolds. Extracellular matrices including collagen I and proteoglycan-like substrate were synthesized, while osteoid and bone-like tissue formed during the culture period. Furthermore, the cell/scaffold constructs had good biomineralization effect after 3 weeks in culture.

Animals↗