BACKGROUND:Developmental dysplasia of hip causes groin pain in patients with prolonged activity or standing due to the presence of deformities of the acetabulum and femoral head in terms of structure,size and orientation,and if not effectively treated,patients' normal activities will be severely limited.OBJECTIVE:Finite element model of the hip joint of solid-liquid biphase fiber reinforced cartilage based on FEBio was established to explore the biomechanical properties of the cartilage for patients with developmental dysplasia of hip and the normal hip joint.METHODS:A patient with developmental dysplasia of hip and a normal volunteer were chosen to build their left hip models including left pelvis,left femur,and cartilage attached thereto. The solid-liquid biphase fiber reinforced cartilage of normal hip was verified to be effective. The cartilage equal contact stress,fluid pressure,solid effective stress,and fluid support rate differences between the developmental dysplasia of hip patients hip and the normal one in the case of one leg of static load (2130 N) were compared after establishing finite element models of developmental dysplasia of hip patients.RESULTS AND CONCLUSION:(1) Compared with the finite element results of the normal hip model,the cartilage contact position of developmental hip dysplasia patient hip showed obvious edge contact,the peak contact stress (3.86 Mpa) and peak fluid pressure (3.76 Mpa) were both higher than normal hip model. (2) After 1500 s (stable load-bearing capacity),peak contact stress and peak fluid pressure in both models decreased,but the cartilage contact position of developmental hip dysplasia patient hip moved from the edge of cartilage to the center,and fluid support rate decreased from 97.41％ to 91.08％. The fluid support rate in normal hip was decreased by 0.58％ from 95.24％ to 94.66％. (3) It is indicated that under the physiological load of standing on one leg,the cartilage of developmental dysplasia of hip patients showed obvious edge load,and the decrease of peak contact stress,fluid pressure,and fluid formation rate was greater than that of normal cartilage. Considering the solid-liquid biphasic fiber reinforcement characteristics of cartilage,it is of great clinical significance to evaluate the biomechanical properties of hip cartilage in developmental dysplasia of hip patients,to understand the pathophysiological mechanism of developmental dysplasia of hip,and make preoperative plan.

Extensive epigenetic reprogramming involves in memory CD8+ T-cell differentiation. The elaborate epigenetic rewiring underlying the heterogeneous functional states of CD8+ T cells remains hidden. Here, we profile single-cell chromatin accessibility and map enhancer-promoter interactomes to characterize the differentiation trajectory of memory CD8+ T cells. We reveal that under distinct epigenetic regulations, the early activated CD8+ T cells divergently originated for short-lived effector and memory precursor effector cells. We also uncover a defined epigenetic rewiring leading to the conversion from effector memory to central memory cells during memory formation. Additionally, we illustrate chromatin regulatory mechanisms underlying long-lasting versus transient transcription regulation during memory differentiation. Finally, we confirm the essential roles of Sox4 and Nrf2 in developing memory precursor effector and effector memory cells, respectively, and validate cell state-specific enhancers in regulating Il7r using CRISPR-Cas9. Our data pave the way for understanding the mechanism underlying epigenetic memory formation in CD8+ T-cell differentiation.
CD8-Positive T-Lymphocytes/metabolism* ; Cell Differentiation ; Chromatin/immunology* ; Animals ; Mice ; Immunologic Memory ; Epigenesis, Genetic ; SOXC Transcription Factors/immunology* ; NF-E2-Related Factor 2/immunology* ; Mice, Inbred C57BL ; Gene Regulatory Networks ; Enhancer Elements, Genetic

Objective To study the chemical constituents of Fallopia aubertii L.Henry Holub. Methods The chemical constituents of Fallopia aubertii L.Henry Holub. were separated and purified by online two-dimensional preparative liquid chromatography and identified by physical and chemical constants and spectral analysis. The inhibitory activities on xanthine oxidase were determined by ultraviolet spectrophotometry. Results Ten compounds were isolated from the extract of Fallopia aubertii L.Henry Holub, including isotachioside（1）, 3,4,5-trimethoxyphenyl-（6'-O-galloyl）-O-β-D-Glucopyranoside（2）, 1-hydroxy-,4,5-1-O-[6'-O-（4''-carboxy-1'',3'',5'trihydrotrimethoxyphenylxy）-phenyl]-β-D-glucopyranoside（3）, myricetrin（4）, myricetin（5）, rutin（6）, quercetin-3-O-β-D-galactoside（7）, quercetin-3-O-β-D-glucopyranoside（8）, lyciumideA（9）, and N-trans-Feruloyltyramine（10）. The inhibitory activity test results showed that the IC₅₀ of compound 5 was 15.92 μmol/L, and the IC₅₀ of compound 6 was 87.36 μmol/L. Conclusion Compounds 1,2,3,4 and 8 were isolated from Medicago polymorpha for the first time. Compounds 5 and 6 had xanthine oxidase inhibitory activity.

The lumbar intervertebral disc exhibits a complex physiological structure with interactions between various segments, and its components are extremely complex. The material properties of different components in the lumbar intervertebral disc, especially the water content (undergoing dynamic change as influenced by age, degeneration, mechanical loading, and proteoglycan content) - critically determine its mechanical properties. When the lumbar intervertebral disc is under continuous pressure, water seeps out, and after the pressure is removed, water re-infiltrates. This dynamic fluid exchange process directly affects the mechanical properties of the lumbar intervertebral disc, while previous isotropic modeling methods have been unable to accurately reflect such solid-liquid phase behaviors. To explore the load-bearing mechanism of the lumbar intervertebral disc and establish a more realistic mechanical model of the lumbar intervertebral disc, this study developed a solid-liquid biphasic, fiber-reinforced finite element model. This model was used to simulate the four movements of the human lumbar spine in daily life, namely flexion, extension, axial rotation, and lateral bending. The fluid pressure, effective solid stress, and liquid pressure-bearing ratio of the annulus fibrosus and nucleus pulposus of different lumbar intervertebral discs were compared and analyzed under the movements. Under all the movements, the fluid pressure distribution was closer to the nucleus pulposus, while the effective solid stress distribution was more concentrated in the outer annulus fibrosus. In terms of fluid pressure, the maximum fluid pressure of the lumbar intervertebral disc during lateral bending was 1.95 MPa, significantly higher than the maximum fluid pressure under other movements. Meanwhile, the maximum effective solid stress of the lumbar intervertebral disc during flexion was 2.43 MPa, markedly higher than the maximum effective solid stress under other movements. Overall, the liquid pressure-bearing ratio under axial rotation was smaller than that under other movements. Based on the solid-liquid biphasic modeling method, this study more accurately revealed the dominant role of the liquid phase in the daily load-bearing process of the lumbar intervertebral disc and the solid-phase mechanical mechanism of the annulus fibrosus load-bearing, and more effectively predicted the solid-liquid phase co-load-bearing mechanism of the lumbar intervertebral disc in daily life.
Humans ; Finite Element Analysis ; Intervertebral Disc/physiology* ; Lumbar Vertebrae/physiology* ; Weight-Bearing/physiology* ; Biomechanical Phenomena ; Stress, Mechanical ; Computer Simulation ; Models, Biological

BACKGROUND:Developmental dysplasia of hip causes groin pain in patients with prolonged activity or standing due to the presence of deformities of the acetabulum and femoral head in terms of structure,size and orientation,and if not effectively treated,patients' normal activities will be severely limited.OBJECTIVE:Finite element model of the hip joint of solid-liquid biphase fiber reinforced cartilage based on FEBio was established to explore the biomechanical properties of the cartilage for patients with developmental dysplasia of hip and the normal hip joint.METHODS:A patient with developmental dysplasia of hip and a normal volunteer were chosen to build their left hip models including left pelvis,left femur,and cartilage attached thereto. The solid-liquid biphase fiber reinforced cartilage of normal hip was verified to be effective. The cartilage equal contact stress,fluid pressure,solid effective stress,and fluid support rate differences between the developmental dysplasia of hip patients hip and the normal one in the case of one leg of static load (2130 N) were compared after establishing finite element models of developmental dysplasia of hip patients.RESULTS AND CONCLUSION:(1) Compared with the finite element results of the normal hip model,the cartilage contact position of developmental hip dysplasia patient hip showed obvious edge contact,the peak contact stress (3.86 Mpa) and peak fluid pressure (3.76 Mpa) were both higher than normal hip model. (2) After 1500 s (stable load-bearing capacity),peak contact stress and peak fluid pressure in both models decreased,but the cartilage contact position of developmental hip dysplasia patient hip moved from the edge of cartilage to the center,and fluid support rate decreased from 97.41％ to 91.08％. The fluid support rate in normal hip was decreased by 0.58％ from 95.24％ to 94.66％. (3) It is indicated that under the physiological load of standing on one leg,the cartilage of developmental dysplasia of hip patients showed obvious edge load,and the decrease of peak contact stress,fluid pressure,and fluid formation rate was greater than that of normal cartilage. Considering the solid-liquid biphasic fiber reinforcement characteristics of cartilage,it is of great clinical significance to evaluate the biomechanical properties of hip cartilage in developmental dysplasia of hip patients,to understand the pathophysiological mechanism of developmental dysplasia of hip,and make preoperative plan.

BACKGROUND:Avascular necrosis of the femoral head is a refractory orthopedic disease that seriously affects the normal life of patients.Hip preservation is recommended for young patients due to the limited prosthesis longevity and revision.Accurate prediction of the mechanical properties of the necrotic area in the early stage and then intervention is the key to hip preservation. OBJECTIVE:To establish a dynamic contact mechanics finite element model of necrotic femoral head based on human hip CT data and predict effects of both necrotic volume magnitude and its position on biomechanics of the necrotic region under walking movement. METHODS:CT data of a volunteer were collected and then geometry model of the hip was rebuilt.Finite element model of the necrotic femoral head was established using the Abaqus software.Nine different necrotic femoral models were constructed by combined both three different necrotic volume magnitudes(small,medium and big volume)and three different necrotic positions(coincided with,medium deviated with and kept away from the line of the force).The Von Mises of the necrotic region for all models were predicted under both 3 000 N static load and dynamical loads of one whole ISO walking gait cycle.The collapse risk for all models was evaluated based on collapse criterion. RESULTS AND CONCLUSION:(1)More approaching of the necrotic region to the line of force and bigger collapse volume made the maximum Von Mises increasing.This also enlarged the collapse risk of the necrotic region.(2)For different load types,walking movement increased the maximum Von Mises of the necrotic region than that of the value under static load under the same necrotic volume and location.(3)In conclusion,dynamic load would result in increasing of the maximum Von Mises of the necrotic region comparing to static load during exercise.Therefore,the risk of local collapse will increase due to greater Von Mises.However,the overall collapse risk is lower than that of static load due to the dynamic change of bearing area.This factor should be carefully considered by surgeons when they evaluate the mechanical performance of the necrotic femoral head.

Objective For patient-specific open-wedge high tibial osteotomy(OWHTO),a novel anatomical fixation plate was designed,and the effects of geometric parameters and material selection on biomechanical fixation were studied.Methods A patient-specific OWHTO anatomical fixation plate was designed and constructed,and the effects of design parameters(thickness,width,and length of the fixation plate)and four different materials(stainless steel,titanium alloy,magnesium alloy,and PEEK)on the biomechanics of the OWHTO fixation system were studied using finite element analysis.The biomechanical differences between the anatomical fixation plate and TomoFix fixation plate were also compared.Results The thickness had a greater effect on the micromotion of the osteotomy space than the length and width of the fixation plate did.Titanium alloy or magnesium alloy fixation plates were more conducive than stainless steel and PEEK materials in obtaining reasonable stability and mechanical transfer simultaneously.Compared with that of the TomoFix plate,the maximum von Mises stress of the anatomical fixation plate was reduced by 13.5%;the maximum von Mises stress of the screws and tibia was increased by 9.8%and 18.4%,respectively;and the micromotion at the maximum osteotomy space cc was increased by 49.3%.Conclusions Anatomical fixation plates have a positive effect on reducing the stress-shielding effect and improving biomechanical properties under the premise of ensuring stability.This study provides a reference for the development of OWHTO anatomical fixation plates.

Objective:To evaluate the mechanical performance of customized metal prosthesis with tibia stems of varying lengths for tibial bone defects reconstruction.Methods:Morphologically matched postoperative finite element models of bone defect revision were developed, with three gradients (15 mm, 30 mm, and 45 mm) according to the degree of bone defect and were reconstructed with 3D printed tantalum metal prosthesis using three tibial stem lengths (80 mm, 120 mm, and 150 mm), respectively. Conventional static and dynamic (walking gait) loading was performed to analyze the peak tibial stress distribution and accumulated sliding distance at the prosthetic interface, and to assess the effects of the three tibial stems of different lengths on the stability of the customized tibial defect restorations and the internal tibial stress state.Results:The peak accumulated sliding distance of the dynamically loaded morphologically matched restorations ranged from 17.94 to 21.31 mm with static loading, which were 68% to 84.3% higher than those of 10.26 to 11.69 mm with static loading. The peak tibial stresses in the dynamically loaded model were greater than those in the statically loaded model, with an increase of 28%-49.2%, including 132.94-143.88 MPa in the statically loaded model and 170.41-200.14 MPa in the dynamically loaded model. The overall accumulated sliding distance of the tibia prosthetic model gradually decreased from the tibial osteotomy surface, and the accumulated peak sliding distances ranged from 10.26 to 11.69 mm for static loading, and from 17.94 to 21.31 mm for dynamic loading. The bone tissue stresses in the anterolateral and medial-posterior tibia increased gradually from top to bottom, and the maximum stress value in each section was in the posterior medial tibia (the maximum value was 200.14 MPa). The highest bone tissue stress in the lateral tibia was affected by the tibial stem length, which resulted in a different location, and it was the area most affected by stress shielding (maximum value of 170.65 MPa).Conclusion:For stability assessment of morphologically matched tantalum customized prosthesis, physiological gait dynamic loading studies are more reliable than static loading; the choice of tibial stem length depends on a combination of accumulated peak sliding distances and tibial bone stress distribution factors.

Hypoxia is the common characteristic of almost all solid tumors,which prevents therapeutic drugs from reaching the tumors.Therefore,the development of new targeted agents for the accurate diagnosis of hypoxia tumors is widely concerned.As carbonic anhydrase Ⅸ(CA Ⅸ)is abundantly distributed on the hypoxia tumor cells,it is considered as a potential tumor biomarker.4-(2-Aminoethyl)benzenesulfo-namide(ABS)as a CA Ⅸ inhibitor has inherent inhibitory activity and good targeting effect.In this study,Ag2S quantum dots(QDs)were used as the carrier to prepare a novel diagnostic and therapeutic bio-probe(Ag2S@polyethylene glycol(PEG)-ABS)through ligand exchange and amide condensation reaction.Ag2S@PEG-ABS can selectively target tumors by surface-modified ABS and achieve accurate tumor im-aging by the near infrared-Ⅱ(NIR-Ⅱ)fluorescence characteristics of Ag2S QDs.PEG modification of Ag2S QDs greatly improves its water solubility and stability,and therefore achieves high photothermal sta-bility and high photothermal conversion efficiency(PCE)of 45.17％.Under laser irradiation,Ag2S@PEG-ABS has powerful photothermal and inherent antitumor combinations on colon cancer cells(CT-26)in vitro.It also has been proved that Ag2S@PEG-ABS can realize the effective treatment of hypoxia tumors in vivo and show good biocompatibility.Therefore,it is a new efficient integrated platform for the diagnosis and treatment of hypoxia tumors.