Modified design of biotype self-locking hip joint prosthesis / 中国组织工程研究

BACKGROUND:Hip prosthesis needs to meet the good structural compatibility with femoral bone marrow cavity and the biomechanical properties of the original bone tissue. However, the difference of individual anatomical characteristics and the stress concentration in the local area after replacement directly affect postoperative combination of femoral prosthesis stem, force flow transfer and femoral reconstruction, and finaly result in aseptic loosening of hip joint in some patients. OBJECTIVE:To analyze the biomechanical characteristics of modified biotype self-locking hip prosthesis by the method of finite element analysis, and to provide the reference for the application of self-locking hip prosthesis in hip replacement. METHODS:Experimental design contained traditional biotype hip joint prosthesis group and self-locking hip joint prosthesis group. In accordance with the finite element models of self-locking hip prosthesis, 28 kinds of screw fixation were established. Three-dimensional models were generated in the Minics system. After the optimization of prosthesis, prosthesis was designed. In the Solidworks software, the femur was re-positioned and set for contacting set in Ansys to analyze the stress distribution and displacement distribution of the femoral-prosthesis-screw by Ansys. We compared the peak of stress and displacement of the femur and prosthesis, and analyzed the biomechanical stability of prosthesis. RESULTS AND CONCLUSION:(1) By using the Ansys finite element method, we analyzed the stress and displacement distribution of the femoral-prosthesis-screw. The minimum stress peak value of the femur was 15.698 MPa. The minimum stress peak value of prosthesis was 45.491 MPa. The minimum stress peak value of screw was 8.359 MPa. The minimum displacement peak value of femur was 1.125 3 mm. The minimum displacement peak value of prosthesis was 1.039 6 mm. The minimum displacement peak value of screw was 0.566 4 mm. (2) Compared with the traditional biotype hip joint prosthesis group, in 28 kinds of self-locking hip joint prostheses, the stress was minimum in the group E. The displacement was minimum in groups A-F. Regarding comprehensive stress and displacement, groups A-F were the best combination. The maximum stress of femoral-prosthesis-screw was 18.936, 59.494 and 12.382 MPa. The maximum displacement of femoral-prosthesis-screw was 1.125 3, 1.039 6 and 0.626 3 mm. (3) These findings indicated that the stress and displacement parameters of groups A-F was the best parameter combination in 28 kinds of self-locking hip joint prostheses, and it is the recommended index of researching and developing self-locking hip prosthesis.

Effect of asymmetry traction on the expression of type II collagen in adult rat condyle / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The aim of this investigation was to study the expression of collagen type II in the cartilage of mandibular condyle following asymmetric inter-maxillary traction.</p><p><b>METHODS</b>Two hundred and twenty SD rats were used in this study (one hundred and four rats loading 0.39 N elastic force, another one hundred and four rats loading 1.18 N elastic force, while twelve rats for control). The extra-joint device was fixed on the right side by surgery. Half of the experimental group was killed at 3, 7, 14, 28 days. The devices were removed at the 28th day in the rest rats, and the rats were sacrificed at 3, 7, 14, 28 days after removing the device. The type II collagen expression levels of all the joints were measured using immunohistochemical techniques.</p><p><b>RESULTS</b>The positive expression of the type II collagen was mainly observed in the cytoplasm of chondrocyte, especially in maturative and hypertrophic layer. The expression intensity was different in different stages and different sides. Both of the two experimental groups showed the same tendency, while the changes in the light force group were more obviously than the heavy force group. In the right side (force-loading side), the type II collagen expression decreased at the early force-loading period. After the device was removed, the expressions increased immediately but then reach the lowest level. The expression almost recovered to normal level at the end of experiment. In the left side (none force-loading side), the expression remained increasing after force-loading and reached the peak at the 14th day.</p><p><b>CONCLUSION</b>These results suggest that even in the adult individuals, the chondrocyte showed reaction to the mechanical force by altering type II collagen expression patterns and it may be the cause of the cartilage remolding after asymmetric inter-maxillary traction. A forward elastic force showed a depressant effect in matrix synthesis, and heavy force had stronger effect. But the rotation of condyle accelerated the matrix synthesis.</p>

Early-response of the condylar chondrocyte under cyclic uniaxial compressive stress / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the protein profile after treatment of the cyclic uniaxial compressive stress on the rat condylar chondrocyte in vitro.</p><p><b>METHODS</b>The third-passage chondrocytes were harvested from the mandibular condyles of 2-day-old rats, and a cellular compressive stress device (self-made four-point bending system) was used to apply stress on cells at 2000 microstrain and 4000 microstrain (0.5 Hz frequency) for 60 min. The early effects of cyclic uniaxial compressive stress on the protein profile of the rat mandibular condylar chondrocytes were examined by two dimensional polyacrylamide gel electrophoresis (2D-PAGE) and matrix-assisted laser-desorption ionization time of flight mass spectrometry (MALDI-TOF-MS).</p><p><b>RESULTS</b>The results showed that the protein profile of the condylar chondrocyte did not change statistically in 2000 microstrain group. In 4000 microstrain group, the protein profile of the condylar chondrocyte was changed. Three new proteins appeared. Five proteins disappeared. Twenty-two proteins were down-regulated and 7 proteins were up-regulated (P < 0.05). The eight different protein spots were identified by MALDI-TOF-MS. It included cytoskeleton protein (gamma-actin and vimentin), glycometabolism protein (alpha enolase and stress-70 protein) and signal transduction protein (Raf kinase inhibited protein, RKLP).</p><p><b>CONCLUSIONS</b>There were significant alternations of the protein profile in the rat condylar chondrocyte after the 4000 microstrain cyclic uniaxial compressive stress loading for 60 min. These different proteins might take part in the early response to the cyclic uniaxial compressive stress.</p>

Early effects of the cyclic uniaxial compressive stress on Actin and Vimentin of the rat condylar chondrocytes / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the early effects of the cyclic uniaxial compressive stress on Actin and Vimentin of the rat condylar chondrocyte.</p><p><b>METHODS</b>The third-passage chondrocyte were harvested from the mandibular condyles of 2-day-old rats, and a cellular compressive stress device was used to apply stress on cells at 4 000 microstrain for 15, 30, 60, 120, 240 min. The early effects of the cyclic uniaxial compressive stress on Actin and Vimentin of the rat mandibular condylar chondrocytes were examined by laser scanning confocal microscope (LSCM), immunofluorescence technique and Western blot.</p><p><b>RESULTS</b>The expression of fluorescent light of cys-toskeleton protein changed obviously with 4000 microstrain compressive stress loading. The expression of Actin significantly decreased in 60 min, and the expression of Vimentin decreased in 30 min. Then the expression of these two protein recovered in 120 min.</p><p><b>CONCLUSION</b>There are time-responsiveness between the 4000 microstrain compressive stress stimulate and Actin, Vimentin. It shows the expression of Actin and Vimentin down-regulated at first under the compressive stress, then increased by feedback. It hints that there are "self-regulate" mechanisms in the cell response to mechanics stimulate.</p>

The expression of TGF-beta1 mRNA in the maxillary sutures of puberty rhesus loaded with the class III intermaxillary orthopedic force / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The purpose of the study is to detect the expression of TGF-beta1 mRNA in the maxillary sutures of puberty rhesus during different periods of the loading of intermaxillary class III orthopedic force.</p><p><b>METHODS</b>The animal model was established with 6 puberty female rhesus, which were randomly divided into experimental group (wearing class III twin-block magnet appliance, each 2 rhesus for 3 and 6 month respectively) and control group (not wearing any appliance, each 1 rhesus for 3 and 6 month respectively). Tissue sections were obtained perpendicular to the sutures. In situ hybridization was used to the expression of TGF-beta1 mRNA, and the expression intensity was measured and statistics was performed by SPSS 11.0.</p><p><b>RESULTS</b>There were no statistic differences of cellular density between palatomaxillary suture in vertical group and pterygomaxillary suture in horizontal group, but statistic differences were found between other groups. The expression of TGF-beta1 mRNA was detected in the control group, but the expression intensity was obviously increased after the load of intermaxillary class III orthopedic force. Statistically significant differences were found among all groups except the six months experimental group and control group of temporozygomatic sutures and pterygomaxillary sutures. Experimental groups were more intensive than the control group and three months group was more intensive than the six months group.</p><p><b>CONCLUSION</b>The active tissue remodeling happened in the circummaxillary sutures by the effect of class III intermaxillary orthopedic force. Cell proliferation, extracellular matrix synthesis and bone formation were accelerated. During the different remodeling periods, the expression intensities were different, which may be related to the different force loading manners, the different reaction of sutures to the orthopedic force and the different biological function of TGF-beta1 in the different periods.</p>

Novel mutations of PAX9 gene in Chinese patients with oligodontia / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the mutational characteristics of PAX9 gene in Chinese patients with congenital oligodontia and thus to provide a molecular basis for studying the pathogenesis of oligodontia.</p><p><b>METHODS</b>Thirteen individuals with oligodontia and 9 healthy individuals, from 4 unrelated autosomal dominant families, and 16 sporadic patients with hypodontia in China, as well as 196 healthy control individuals (without oligodontia or hypodontia) were screened. Congenital absence of teeth was confirmed by panoramic X-ray analysis. Mutations of PAX9 gene were detected using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. After the finding of abnormal SSCP bands, analysis was carried out with DNA sequencing.</p><p><b>RESULTS</b>PCR-SSCP detected SSCP bands alteration in exon2 of PAX9 gene in two unrelated families. Sequencing of PAX9 gene revealed a novel frameshift mutation (109InsG) and a novel missense mutation (C139T). All the affected members of each family were heterozygous for the mutations. In sporadic patients and the other two families, no similar sequence changes in PAX9 gene were found.</p><p><b>CONCLUSIONS</b>The results extend the spectrum of mutations in PAX9 gene associated with oligodontia. The novel mutations will play an important role in gene diagnosis of oligodontia.</p>

Functional analysis of novel mutations in PAX9 associated with familial oligodontia / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To gain new insights into the molecular pathogenesis of the 109(InsG) and 139(C--> T) mutations and their roles in familial oligodontia.</p><p><b>METHODS</b>The region of PAX9 paired domain (PAX9PD) was amplified and the expression plasmids were constructed in pGEXlambda -1T by PCR-based cloning. PAX9PD proteins were prepared on the basis of GST instruction. The binding of wild type and two novely mutant PAX9 paired domain to double-stranded DNA targets were analyzed by gel mobility shift assay.</p><p><b>RESULTS</b>Wild type PAX9PD protein bind to the high affinity paired domain recognition sequences, CD19-2(A-ins) and Pax6CON, the 109(InsG) and 139(C--> T) mutant PAX9PD protein were unable to bind to these cognate DNA-binding sites.</p><p><b>CONCLUSION</b>The functional defects in DNA binding of mutant 109(InsG) PAX9 and 139(C--> T) PAX9, as well as loss-of-function of PAX9 most likely result in its haploinsufficiency during the patterning of dentition and the subsequent loss of posterior teeth.</p>

The expression of TGF-beta 1 mRNA in pubescent rhesus monkeys' condyle under Class III intermaxillary functional orthopedic force / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the expression of TGF-beta 1 mRNA in pubescent Rhesus monkeys' condylar under Class III intermaxillary functional orthopedic force for different lengths of time.</p><p><b>METHODS</b>Six pubescent Rhesus monkey were divided into two test groups and a control group. Monkeys in the test groups were TMAIII while the control groups did not. Histological method (HE staining) and in situ hybridization were employed in this study.</p><p><b>RESULTS</b>1. The histological results showed that, compared with the control group, the anterior part of the condyle became thicker while the median part and the posterior part became thinner in 3 months group. However, in 6 months group, the change was similar to 3 months group. 2. The results of in situ hybridization showed that, in control group, TGF-beta 1 mRNA mildly expressed in the anterior part of the condyle while extensively in the median and posterior parts. In 3 months group, TGF-beta 1 mRNA expressed in all parts of condyle; the most intensive expression was in the anterior part. Compared with 3 months group, the expression of TGF-beta 1 mRNA decreased in 6 months group, but the expression in anterior part was stronger than in median and posterior parts.</p><p><b>CONCLUSION</b>Under Class III Orthopedic therapy, TGF-beta 1 mRNA probably participated in the endochrondral bone remodeling in the condyle, and the expression was closely related to loading time. In 3 months group, the expression of TGF-beta 1 mRNA was stronger than that in 6 months group. It was inferred that the remodeling of endochrondral bone was more active in 3 months group.</p>