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As a kind of elastic load-bearing connective tissues on bone surface in dynamic joints, articular cartilage can provide low wear lubrication, shock absorption, load transfer and other supporting functions, and has hierarchical fiber composite structures and excellent mechanical properties. As an avascular and aneural tissue,the degenerated articular cartilage lacks the capability of self-healing after damage. The high incidence of arthritisis still a hot spot in basic and clinical researches. Articular cartilage is a mechanical sensitive tissue, andmechanical environment will affect the development of tissues in different directions. Extensive researches onbiomechanics and mechanobiology of articular cartilage were conducted in 2022. Many studies on morphology, function and mechanical state of cartilage,as well as mechanical state of cartilage under different conditions were reported. Some cartilage-related loading devices were designed at animal, tissue and cell levels. Researches onthe repair of cartilage degeneration and injury under mechanical loads were carried out in vitro and in vivo, andsome important repair method and means were obtained. The biomechanical and mechanobiology research on articular cartilage is the basis of arthritis, cartilage defect and repair. The influence of quantitative mechanical under 4 conditions on the repair of articular cartilage injury needs further study in vivo and in vitro
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@#Introduction: A posterior horn medial meniscus (PHMM) tear subjects the knee to pathological stresses, especially in the setting of a deficient anterior cruciate ligament (ACL). These PHMM tears have to be surgically addressed, however they remain a diagnostic challenge. Hence, this study aims to evaluate the wave sign as an arthroscopic diagnostic aid for the PHMM tear which may be occult. Materials and methods: This is a retrospective study of 61 consecutive patients (62 ACL-deficient knees) who underwent arthroscopic primary ACL reconstruction between September 2017 and August 2018. We defined PHMM tears as tears located in the posterior one-third of the medial meniscus. Root tears and ramp lesions were included in our analysis. The arthroscopic findings were recorded after a comprehensive arthroscopic survey. Results: In the sample of ACL-deficient knees, 44 (71.0%) had a concomitant medial meniscus tear. The most common location for the tear was in the posterior horn (81.8%). There were seven occult PHMM tears, not described by the radiologist or identified by the operating surgeon on the preoperative magnetic resonance imaging. The wave sign was identified in 10 (16.1%) knees, all confirming the presence of the PHMM tear. A positive correlation was found between the presence of the wave sign and the PHMM tear. Conclusions: The wave sign has a statistically significant but weak positive correlation with the presence of the PHMM. We view the wave sign as a valuable arthroscopic cue to rule-in the presence of the PHMM tear in the ACLdeficient knee.
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Objective:To investigate the adhesion of polydopamine-modified collagen membrane composites to cartilage tissues and the effect on chondrocyte proliferation, and further explore the possibility of their application in autologous chondrocyte transplantation.Methods:Porous collagen membranes were prepared, and the polydopamine-modified collagen membrane composites were constructed by the adsorption method. The physical and chemical properties and structural characteristics of the membranes, such as thermal stability, thermal properties, porous structure, and surface element composition, were characterized by infrared spectroscopy, thermogravimetric analysis, differential thermal analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy, respectively. The adhesion between the polydopamine-modified collagen membrane and fresh cartilage tissue was tested by a mechanical testing machine. The effects of the membranes on the adhesion and proliferation of rabbit chondrocytes were investigated by in vitro cell culture.Results:The structure and surface element composition of the membranes altered with the increase in the adsorption time of polydopamine, and the capacity of polydopamine increased with the increase in the adsorption time. The thermal stability and thermal properties of collagen membrane materials were not significantly affected by the adsorption of polydopamine. The adhesion of the membrane to cartilage tissue increased with the increase in the amount of absorbed polydopamine. The membranes showed a time-dependent promoting effect on the proliferation of the chondrocytes.Conclusions:The polydopamine-modified collagen membrane has potential application in articular cartilage repair, but more research is required to optimize the membrane before it is used in articular cartilage repair.
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Cartilage surface fibrosis is an early sign of osteoarthritis and cartilage surface damage is closely related to load. The purpose of this study was to study the relationship between cartilage surface roughness and load. By applying impact, compression and fatigue loads on fresh porcine articular cartilage, the rough value of cartilage surface was measured at an interval of 10 min each time and the change rule of roughness before and after loading was obtained. It was found that the load increased the roughness of cartilage surface and the increased value was related to the load size. The time of roughness returning to the initial condition was related to the load type and the load size. The impact load had the greatest influence on the roughness of cartilage surface, followed by the severe fatigue load, compression load and mild fatigue load. This article provides reference data for revealing the pathogenesis of early osteoarthritis and preventing and treating articular cartilage diseases.
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Animals , Cartilage, Articular , Fatigue , Osteoarthritis/pathology , Pressure , SwineABSTRACT
【Objective】 To discuss the repair effect of lyophilized platelet lysate (PL) products on articular cartilage injury model of rats. 【Methods】 A total of 25 SD rats were injected with typeⅡcollagenase at the right knuckle articular cavity respectively on day 1, 3 and 5 of experiment, and the modeling conditions were observed 14 days after the last injection of collagenase. The SD rats with successful modeling were randomly divided into three groups, and were injected with lyophilized PL [Group A, 1 mL/(mouse·time)], PL [Group B, 1 mL/(mouse·time)], and normal saline[Group C, 1 mL/(mouse·time)]. The above three substances were injected with corresponding drugs on day 0, 7, 14 and 21 of experiment based on the grouping conditions, and the changes of knee joint diameters of the rats from the three groups were observed and compared. On day 14 and 28, one rat in each group was randomly killed and two knuckle articular cavities of each were taken for tissue sampling, using hematoxylin-eosin staining (HE) and immunohistochemistry. 【Results】 After 14 days of modeling by injection of type Ⅱ collagenase, the proportion of successful modeling in rats was 84% (21/25), with the knee joint diameter (mm) before and after modeling at 12.84±1.14 vs 14.11±1.17(P<0.01). On day 14, 21 and 28, groups A and B were superior to group C in the knee joint diameter and activity improvement (P<0.05), with 13.33±1.16 vs 13.37±1.08 vs 14.21±1.08, 13.10±1.09 vs 13.01±1.04 vs 14.09±1.09 and 12.38±1.08 vs 12.51±1.03 vs 14.01±1.07, respectively. Histological observation showed that group A and B were superior to group C in the production and arrangement of chondrocytes and the positive expression of type Ⅱ collagen, and there was no significant difference between group A and group B. 【Conclusion】 The lyophilized PL has similar therapeutic effect to PL in the treatment and repair of articular cartilage injury, and is worthy of clinical application.
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Objective To investigate the distribution of streaming potential generated by interstitial fluid flow in articular cartilage and obtain electrical characteristics of articular cartilage. Methods The governing equation of fluid and electrostatic theory were combined to establish a two-dimensional (2D) micro-element model of cartilage, and the steady streaming potential generated in microelement under certain pressure was calculated by finite element method. Results The streaming potential in micro-pore model of articular cartilage with the length of 5 μm was about 38.4 μV. The effect of external pressure and Zeta potential on streaming potential of articular cartilage model was significant and showed a linear increase relationship. The streaming potential decreased with the increase of ion number concentration, but the concentration had different effects on streaming potential of articular cartilage. When the ion number concentration was low, streaming potential was more dependent on ion number concentration. When ion number concentration was high, the effect of ion number concentration on streaming potential was very small. Conclusions The results of this study provide important theoretical basis for differentiation and proliferation of chondrocytes, prevention and treatment of articular cartilage diseases, development of tissue-engineered cartilage and repair of articular cartilage injury by means of electric current, electric field and electromagnetic field stimulation.
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OBJECTIVE@#To observe the effect of needle knife on chondrocyte autophagy and expressions of autophagy-related protein and mammalian target of rapamycin (mTOR) in rats with knee osteoarthritis (KOA), and to explore the possible mechanism of needle knife for KOA.@*METHODS@#A total of 42 SD rats were randomly divided into a normal group, a model group and a needle knife group, 14 rats in each group. Except for the normal group, the other two groups were injected with the mixture of papain and L-cysteine into the left hind knee joint to establish the KOA model. After modeling, the rats in the needle knife group were treated with needle knife at strip or nodule around the quadriceps femoris and medial and lateral collateral ligament on the affected side, once a week for 3 times (3 weeks). The changes of left knee circumference in each group were observed; the chondrocytes and ultrastructure of left knee joint were observed by HE staining and electron microscope; the mRNA and protein expressions of autophagy-related genes (Atg5, Atg12, Atg4a), Unc-51 like autophagy activated kinase 1 (ULK1), autophagy gene Beclin-1 and mTOR in left knee cartilage were detected by real-time fluorescence quantitative PCR and Western blot.@*RESULTS@#After modeling, the left knee circumferences in the model group and the needle knife group were increased compared with those before modeling and in the normal group (P<0.05); after intervention, the left knee circumference in the needle knife group was smaller than that in the model group and after modeling (P<0.05). Compared with the normal group, the number of chondrocytes was decreased, and a few cells swelled, nuclei shrank, mitochondria swelled and autophagosomes decreased in the model group; compared with the model group, the number of chondrocytes was increased , and most cell structures returned to normal, and autophagosomes was increased. Compared with the normal group, the mRNA and protein expressions of Atg5, Atg12, Atg4a, Beclin-1 and ULK1 in the knee cartilage in the model group were decreased (P<0.05); compared with the model group, the expressions of the above indexes in the needle knife group were increased (P<0.05). Compared with the normal group, the mRNA and protein expressions of mTOR in the knee cartilage in the model group were increased (P<0.05); compared with the model group, the expressions of the above indexes in the needle knife group were decreased (P<0.05).@*CONCLUSION@#The needle knife intervention could improve knee cartilage injury in rats with KOA, and its mechanism may be related to reducing the expression of mTOR and up-regulating the expressions of Atg5, Atg12, Atg4a, ULK1 and Beclin-1, so as to promote chondrocyte autophagy and delay the aging and degeneration of chondrocytes.
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Animals , Rats , Autophagy , Autophagy-Related Protein-1 Homolog/genetics , Beclin-1/genetics , Chondrocytes , Osteoarthritis, Knee/therapy , Rats, Sprague-Dawley , TOR Serine-Threonine Kinases/geneticsABSTRACT
SUMMARY: The Q-angle is defined as the acute angle formed by the vectors for combined pull of the quadriceps femoris muscle and the patellar tendon. This study aimed to investigate the variations in Q angle with respect to race. Moreover, this study performed ultrasound to evaluate of the thickness of articular cartilage covering the medial and lateral femoral condyle in volunteers with an increased Q angle. The study included 487 Jordanian and 402 Malaysians with age range 18-23 years. Moreover, the study included 30 participants aged between 18 and 22 years, with a total of 15 volunteers with Q >14° and 15 patients with Q ≤14°. Both Q angle and condylar distance were measured by well-trained medical practitioners according to a well-established protocol. The thickness of articular cartilage covering the medial and lateral femoral condyle of the femoral bone was measured using ultrasound. Regardless of race, Q angle was greater in females. Furthermore, Q angle was significantly greater in Arab volunteers compared to Malay volunteers. Q angle significantly increase with increasing condylar distance in both races. Finally, the statistical analysis showed a significantly reduced thickness of articular cartilage on both medial and lateral femoral condyle (P = 0.05) in the Q >14° group. Multiple factors including race and condylar distance and even the articular cartilage of femoral condyle should be considered during the examination and management of knee fractures and condylar diseases.
RESUMEN: El ángulo Q se define como el ángulo agudo formado por los vectores de tracción combinada del músculo cuádriceps femoral y el tendón patelar. Este estudio tuvo como objetivo investigar las variaciones en el ángulo Q con respecto a la raza. Además, se realizó una ecografía para evaluar el grosor del cartílago articular que cubre los cóndilos femorales medial y lateral en voluntarios con un ángulo Q aumentado. El estudio incluyó a 487 jordanos y 402 malayos con un rango de edad de 18 a 23 años. Además, el estudio incluyó a 30 participantes con edades comprendidas entre 18 y 22 años, 15 voluntarios con Q> 14 ° y 15 pacientes con Q ≤ 14 °. Tanto el ángulo Q como la distancia condilar fueron medidos por médicos bien entrenados de acuerdo con un protocolo establecido. El grosor del cartílago articular que cubre los cóndilos femorales medial y lateral del fémur se midió mediante ecografía. Independientemente del grupo racial, el ángulo Q fue mayor en las mujeres. Además, el ángulo Q fue significativamente mayor en los voluntarios árabes en comparación con los voluntarios malayos. El ángulo Q se aumenta significativamente al incrementarse la distancia condilar en ambas grupos raciales. Finalmente, el análisis estadístico mostró una reducción significativa del grosor del cartílago articular en los cóndilos femorales medial y lateral (P = 0,05) en el grupo Q> 14. Durante la exploración y el tratamiento de las fracturas de rodilla y de las enfermedades condilares, se deben considerar múltiples factores, incluida la raza y la distancia condilar e incluso el cartílago articular del cóndilo femoral.
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Humans , Male , Female , Adolescent , Young Adult , Cartilage, Articular/diagnostic imaging , Race Factors , Knee/diagnostic imaging , Cartilage, Articular/anatomy & histology , Retrospective Studies , Ultrasonography , Jordan , Knee/anatomy & histology , MalaysiaABSTRACT
Abstract Objective To evaluate clinically and radiologically the results of the treatment of chondral lesions using collagen membrane - autologous matrix-induced chondrogenesis (AMIC). Methods This is a series of observational cases, in which 15 patients undergoing AMIC were analyzed. The clinical evaluation was made by comparing the Lysholm and International Knee Document Commitee (IKDC) scores in the pre- and postoperative period of 12 months, and radiological evaluation using the Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) score in the same postoperative period. Results The mean age of the patients was 39.2 years old, and the mean size of the chondral lesions was 1.55cm2. There was a significant improvement in clinical scores, with a mean increase of 24.6 points on Lysholm and of 24.3 on IKDC after 12 months. In the radiological evaluation, MOCART had a mean of 65 points. It was observed that the larger the size of the lesion, the greater the improvement in scores. Conclusion Evaluating subjective clinical scores, the treatment of chondral lesions with the collagen membrane showed good results, as well as the evaluation of MOCART, with greater benefit in larger lesions.
Resumo Objetivo Avaliar clínica e radiologicamente os resultados do tratamento das lesões condrais com a membrana de colágeno - condrogênese autóloga induzida por matriz. Métodos Trata-se de uma série de casos observacional, na qual foram analisados 15 pacientes submetidos a condrogênese autóloga induzida por matriz. A avaliação clínica foi feita comparando os escores de Lysholm e International Knee Document Commitee (IKDC, na sigla em inglês) no pré- e pós-operatório de 12 meses, e avaliação radiológica através do escore de Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART, na sigla em inglês) no mesmo período de pós-operatório. Resultados A média de idade dos pacientes foi 39,2 anos, e a média do tamanho das lesões condrais foi de 1,55cm2. Houve uma melhora significativa nos escores clínicos, com média de aumento de 24,6 pontos no Lysholm e de 24,3 no IKDC, após 12 meses. Na avaliação radiológica, o MOCART teve média de 65 pontos. Observou-se que quanto maior o tamanho da lesão, maior foi a melhora nos escores. Conclusão Avaliando escores clínicos subjetivos, o tratamento das lesões condrais com a membrana de colágeno mostrou bons resultados, assim como a avaliação de MOCART, com maior benefício em lesões maiores.
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Humans , Male , Female , Adolescent , Adult , Middle Aged , Postoperative Period , Magnetic Resonance Spectroscopy , Cartilage, Articular , Collagen , Chondrogenesis , Knee InjuriesABSTRACT
BACKGROUND: Domestic and foreign scholars have done a lot of researches on the stress of articular cartilage under different mechanical environments and cyclic compressive loads, but they mainly studied the effect of cartilage under the cyclic compressive load. Studies on the effects of age factor on the mechanical properties of cartilage and studies regarding the properties of cartilage in complex stress environments are not exhaustive. OBJECTIVE: To investigate the effects of different rolling load conditions on the ratcheting behavior of adult and juvenile articular cartilage. METHODS: Adult cartilage and juvenile cartilage were used as experimental objects, and the load was applied by a rolling load device under different experimental conditions (compression: 10%, 20%, 30%; rolling rate: 1.66, 3.44, 6.68 mm/s; defect width: 1, 2,4 mm). At the same time, non-contact digital technology was used to collect the sample during the loading process, and the cyclical pressure was studied by analyzing and processing the image. The ratcheting behavior of adult and juvenile articular cartilage was studied under rolling load. RESULTS AND CONCLUSION: Under rolling load, the ratcheting strain of adult cartilage and juvenile cartilage showed a rapid increase followed by a slow increase tendency with the rolling load. With the increase of compression, the ratcheting strain of adult cartilage and juvenile cartilage increased. At the same amount of compression, the ratcheting strain of juvenile cartilage was greater than that of adult cartilage, and their ratcheting strain gradually decreased from the surface layer to the deep layer along the depth of cartilage. As the rolling rate increased, the ratcheting strain of adult cartilage and juvenile cartilage decreased. The ratcheting strain values and trends of 1 mm microdefect articular cartilage were similar to those of intact articular cartilage. Under the condition of 2,4 mm defect, the ratcheting strain value of the defected cartilage was higher than that of the intact cartilage.
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BACKGROUND: Icariin is the main effective component of Epimedium, which functions to tonify the kidney, and strengthen tendons and bones. In recent years, a large number of studies have found that icariin plays a significant role in the treatment of osteoarthritis. OBJECTIVE: To review the research progress in the molecular mechanism of icariin in the treatment of osteoarthritis. METHODS: The first author used “Icariin, Osteoarthritis, Cartilage, Subchondral bone, Synovial membrane, synovium, Inflammation" as search words in English and Chinese to search PubMed, CNKI, WanFang, and VIP databases. According to the inclusion criteria and exclusion criteria, 42 articles were included for final analysis. RESULTS AND CONCLUSION: Icariin can promote the cartilage differentiation of bone marrow mesenchymal stem cells and enhance the proliferation of cartilage cells and osteoblasts, to inhibit the degradation of cartilage extracellular matrix, reduce the activity of osteoclasts and alleviate synovial inflammation caused by inflammatory factors. It is an effective treatment for osteoporosis. However, the optimal effective dose and concentration safety of icariin still need a large number of experimental studies. Currently, most of the experiments are still in animal and tissue cell experiments. Numerous clinical studies are needed to continue to explore its specific mechanism in order to provide evidence-based medical evidence for icariin in the treatment of osteoarthritis.
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BACKGROUND: Anterior cruciate ligament (ACL) reconstruction can restore the stability of knee joint, reduce the mechanical stress on meniscus and cartilage, and avoid the occurrence and development of secondary injury including traumatic arthritis. However, some studies have shown that ACL reconstruction cannot completely prevent the occurrence and development of osteoarthritis, and significant changes in osteoarthritis can be found in the long-term imaging examination after operation. Therefore, there is still controversy about the role of ACL reconstruction in preventing secondary cartilage damage and secondary osteoarthritis, and the changes in cartilage after ACL reconstruction, especially at early stage after ACL reconstruction, have not been fully elucidated. OBJECTIVE: To analyze articular cartilage changes during arthroscopic anterior cruciate ligament reconstruction and second-look arthroscopic evaluation. METHODS: From July 2015 to July 2016, 50 cases of ACL reconstruction with hamstring tendon and second-look arthroscopic exploration were analyzed retrospectively. The cartilage damage and healing between the ACL reconstruction and second-look exploration were recorded. At the same time, the influence of age on articular cartilage was analyzed. The study protocol was approved by the Ethics Committee of Foshan TCM Hospital with an approval No. 20160315. RESULTS AND CONCLUSION: No infection, graft absorption and other complications occurred in all patients. During the second-look exploration, the Lysholm score, International Knee Documentation Committee evaluation score, Tegner score and KT-1000 lateral difference were significantly improved compared with those before operation (P 0.05). During the second-look exploration, the patients with anterior cruciate ligament reconstruction who were 30 years old and above had significantly worse subpatellar, trochlear, medial femoral condyle, lateral femoral condyle and tibial lateral platform cartilage tissues than those under 30 years (P < 0.05). The results suggest that the reconstruction of ACL with autogenous hamstring tendon can achieve better stability and function of the knee joint. However, even in the early postoperative period, osteoarthritis is still progressing. Therefore, it is necessary for patients with ACL reconstruction to pay attention to the progression of osteoarthritis and the appearance of knee joint symptoms.
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BACKGROUND: Articular cartilage degeneration is the main cause of osteoarthritis. Bone morphogenetic proteins play an important role in cartilage regeneration and repair. OBJECTIVE: To review the research progress of bone morphogenetic protein in the process of articular cartilage regeneration. METHODS: A computer-based online search of PubMed and Elsevier databases was performed using the keywords “bone morphogenetic proteins, BMPs, arthritis, osteoarthritis, OA, cartilage, chondrocyte” in English. A total of 272 papers were retrieved, 96 of which were included in final analysis. Another 27 papers related to concepts were also included. Therefore, 123 papers are finally included. RESULTS AND CONCLUSION: Bone morphogenetic proteins participate in many biological processes including cell proliferation, differentiation, migration, and apoptosis, and play an important role in the formation of bone and cartilage. Bone morphogenetic proteins participate in a variety of signaling pathway cascades by binding to different receptors, which can protect articular cartilage from cartilage destruction caused by inflammation and trauma. Bone morphogenetic proteins alone or in combination with other cytokines can repair cartilage defects improve degenerative lesions, and promote the differentiation and regeneration of articular chondrocytes. However, there are still some practical problems that need to be solved for the widespread use of bone morphogenetic proteins in cartilage regeneration, such as the safety of drug transporters, the lack of effective biological scaffold materials, the optimal dosage and time point of use of biological agents, and their toxic and side effects. Future research will focus on how to solve the above problems. The widespread application of bone morphogenetic proteins will open a new era for targeted treatment of cartilage damage and cartilage degenerative diseases represented by osteoarthritis.
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With extraordinary mechanical properties, articular cartilage is one of the most critical factors in human movement and load transmission. With the increase of sports participation and population aging, more and more patients suffer from cartilage injury and related diseases. Accurate acquisition of mechanical properties for articular cartilage is the key process of cartilage injury and functional evaluation. In this paper, the research progress of indirect estimation for mechanical properties of articular cartilage was summarized. Furthermore, some new perspectives were prospected on mechanical characterization of articular cartilage.
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The human homologue of mouse progressive ankylosis protein(ANKH)is an inorganic pyrophosphate transport regulator,which regulates tissue mineralization by controlling the level of inorganic pyrophosphate.It plays an important role in the pathogenesis and development of bone and joint diseases,such as ankylosing spondylitis,craniometaphyseal dysplasia,and articular cartilage calcification.This review summarizes the progress of research on ANKH and the above-mentioned diseases.
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Humans , Mice , Ankylosis , Hyperostosis , Hypertelorism , Joint Diseases , MutationABSTRACT
Osteoarthritis (OA) is a chronic degenerative joint disease characterized by joint pain and stiffness, which predisposes to the elderly. The onset of OA is slow, the course of disease is long, and the early clinical manifestations and histological changes are not obvious, which limits the early diagnosis and treatment of the disease. The micro-structure of articular cartilage determines the macro-mechanical properties of cartilage. The micro-structure of articular cartilage changes in a depth-dependent manner, which makes the mechanical properties of cartilage also depth-dependent. From superficial to deep areas of cartilage, the anti-load and anti-deformation ability of cartilage increases gradually. However, with development of the disease, the change of cartilage micro-structure leads to the decrease in load resistance and deformation resistance of OA cartilage. Therefore, the mechanical properties of articular cartilage can be inferred by detecting the micro-structure of articular cartilage. On the other hand, the mechanical properties of articular cartilage can be used to understand the micro-changes of cartilage, which is helpful to understand OA development and facilitate early diagnosis of the disease. This paper reviewed the recent research literatures on mechanical properties of articular cartilage under normal and acute or chronic injuries, and elaborated the relationship between the structure and mechanical properties of articular cartilage, which further provided the theoretical basis for the OA development, early diagnosis and treatment.
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Objective To study the effects of collagen fiber bundle on mechanical properties of articular cartilage, so as to provide references for clinicians to guide the rehabilitation of patients with early cartilage injury. Methods The two-dimensional (2D) numerical model of fiber-reinforced porous viscoelasticity was established, with consideration of the relationship of fiber distribution, elastic modulus, porosity and permeability with cartilage depth. The influences from local fracture of the fiber bundle, the progressive fracture from the surface and the fiber bundle size on mechanical properties of the cartilage were studied, and the maximum principle strain of cartilage matrix was obtained. Results The maximum principal strain of the matrix occurred at a position in middle layer of the cartilage, about upper 1/3 of the cartilage, which was not affected by fiber breakage mode and fiber bundle size. The strain of the cartilage with thicker fiber bundles decreased. Conclusions The middle layer of the cartilage was prone to mechanical damage. The thicker fiber bundle could reduce the maximum principal strain of the matrix. Once the fiber bundle broke, the maximum principal strain of the cartilage matrix with thicker fiber bundle became larger, leading to an easier evolution of the cartilage damage.
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Aging is a major risk factor for diseases such as osteoarthritis (OA) and osteoporosis. However, they are not necessarily the results of aging, and the relationship between changes in bone and cartilage associated with aging and disease progression is still unclear. Studies have shown that the development and progression of OA is not a simple cartilage wear process, while its occurrence involves complex biological, chemical and mechanical changes in the tissues of the entire joint, especially the interaction of mechanics and biochemistry between cartilage and subchondral bone. Aging contributes to the occurrence and development of OA, but it is not the cause of OA. Changes associated with aging provide a foundation for OA to start, making joints more susceptible to other factors such as abnormal biomechanics and biochemistry, thereby promoting the development of OA. Therefore, understanding the basic mechanisms by which aging affects joint tissue may provide new targets for slowing or preventing the development of OA. In this paper, the related research progresses are reviewed from three aspects, i.e. age-related changes in cartilage and subchondral bone, mechanical conduction and angiogenesis.
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BACKGROUND: Once the articular cartilage has a crack defect, its mechanical properties will change. In previous studies, the investigation of damaged articular cartilage mostly focused on compression, and there were few studies on tensile properties. OBJECTIVE: To measure the uniaxial quasi-static tensile properties by preparing crack defects on the cartilage layer samples. METHODS: The articular cartilage of the fresh adult pig knee joint was selected to prepare a cartilage specimen containing a crack defect. The tensile properties were tested at different stress rates (0.001, 0.01 and 0.1 MPa/s) and the creep properties were tested under different constant stresses (1, 2 and 3 MPa). RESULTS AND CONCLUSION: (1) In the tensile test at different stress rates, as the stress rate increases, the stress required to reach the same strain increased gradually, and the Young's modulus of the test piece increases with the increase of the stress rate. (2) The tensile stress-strain curves of the articular cartilage with cracks at different stress rates did not coincide, indicating that the tensile properties of the articular cartilage with crack defects are rate-dependent. (3) In the creep experiment under different constant tensile stress levels, the creep strain increased with the increase of the tensile stress level, the creep compliance decreased with the increase of the tensile stress level, and with the creep time. The creep strain increased rapidly and then increased slowly. (4) To conclude, different stress rates and different constant stresses have great influence on the tensile mechanical properties of articular cartilage with crack defects. The experimental results provide a mechanical reference for the repair of defective articular cartilage.
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BACKGROUND: Osteoarthritis is a refractory degenerative disease that seriously affects patients’ quality of life, and brings a heavy financial burden to their families. Nowadays, treatments for osteoarthritis can only alleviate symptoms, improve joint function in a short period of time, but cannot prevent or reverse the pathological process of osteoarthritis. To date, there are no prophylactic or regenerative therapies for osteoarthritis. The signaling pathway can explain the occurrence and development of disease at the molecular level. Therefore, the regulation of signaling pathway can be used as a potential treatment for osteoarthritis. OBJECTIVE: To review the occurrence and development of osteoarthritis, aiming at providing new ideas for clinical diagnosis, treatment and deeper understanding of diseases in the future. METHODS: CNKI, Wanfang, VlP, CBMdisc, PubMed and MEDLINE databases were retrieved respectively with the keywords of “osteoarthritis; signaling pathway; EGFR; Hedgehog; NF-kB; Notch” in Chinese and English, and included literature reports regarding the signaling pathways related to osteoarthritis published in 2008-2019 were retrieved. RESULTS AND CONCLUSION: Normal articular cartilage function depends on the regulation of multiple signaling pathways, and the occurrence and development of osteoarthritis are also regulated by corresponding signaling pathways, providing deep understanding of osteoarthritis at the molecular level and new ideas for clinical diagnosis and treatment. Regulation of signaling pathways through drug action and gene modification is a potential treatment for osteoarthritis. However, there is a common problem in related research: most of the research on signaling pathway is isolated, and the occurrence and development of osteoarthritis may involve the joint action of multiple signal pathways. Therefore, further research is needed on the synergy of signaling pathways.